docs: update template creation docs for template builder (#26993)

## Summary

Update documentation across 9 files to present the template builder as
the primary template creation method, replacing the old starter
templates flow as the default entry point.

The template builder is a guided wizard that lets admins select base
infrastructure, add registry modules, configure variables, and produce
validated Terraform without writing HCL.

## Changes

**Primary docs (significant rewrites):**
- `docs/admin/templates/creating-templates.md`: Added "Using the
template builder" as the first section with full 5-step wizard
documentation, screenshots, airgap/registry notes, and alternative
creation links. Moved CLI starter template flow to its own section.
Fixed "You can the" typo.
- `docs/get-started/index.md`: Rewrote Steps 4-6 to use the builder with
the Docker base template instead of the Coder Quickstart (which is not a
builder base template). Generalized workspace parameter instructions.
- `docs/start/first-template.md`: Rewrote to use the builder. Removed
old starter templates references, TODO notes, typo, and commented-out
sections.

**Secondary docs (targeted edits):**
- `docs/admin/templates/index.md`: Replaced starter templates section
with builder-first "Create a template" section.
- `docs/admin/templates/managing-templates/index.md`: Renamed "Starter
templates" to "Creating templates" pointing to the builder.
- `docs/install/airgap.md`: Added "Template builder" section documenting
`CODER_DISABLE_TEMPLATE_BUILDER` and
`CODER_TEMPLATE_BUILDER_REGISTRY_URL`.
- `docs/tutorials/template-from-scratch.md`: Added TIP callout
recommending the builder. Fixed `coder templates create` -> `coder
templates push` inconsistency.
- `docs/admin/integrations/devcontainers/envbuilder/add-envbuilder.md`:
Updated Dashboard tab to reference the builder and "Upload an existing
template" alternative.
- `docs/about/screenshots.md`: Updated caption and image reference for
template builder.

**Screenshots added:**
- `templatebuilder_01_bases.png` (base selection step)
- `templatebuilder_02_modules.png` (module selection step)
- `templatebuilder_03_module_customization.png` (module settings step)
- `templatebuilder_04_customizations.png` (template customizations step)

<details>
<summary>Implementation plan</summary>

# Plan: Update docs/ for Template Builder Launch

## Summary

The Template Builder is a new guided wizard at `/templates/new/builder`
that lets admins create templates by selecting a base infrastructure
template, composing it with registry modules, configuring variables, and
producing a validated Terraform bundle without writing HCL. The docs
need to be updated to present this as the primary/recommended template
creation path, while preserving the existing paths (upload, CLI,
duplicate) as alternatives.

## Key behavioral facts from the code

- **Route**: `/templates/new/builder` (new), `/templates/new` (old,
still exists)
- **Entry point**: The "New Template" button on the Templates page links
to `/templates/new/builder` when the builder is enabled; otherwise falls
back to `/starter-templates`
- **5-step wizard**:
  1. **Select base infrastructure** (e.g., Docker, AWS EC2, Kubernetes)
  2. **Base template parameters** (optional, skipped if base has none)
3. **Select modules** (IDE, AI Agent, Source Control, etc.;
multi-select, grouped by category)
4. **Module settings** (optional, skipped if no configurable variables)
5. **Template customizations** (name, display name, description, icon,
organization)
- **Alternative creation links** are shown on step 1: "Start from
scratch", "Upload an existing template", "Browse community templates",
"Use template agent skill"
- **Disabled via**: `CODER_DISABLE_TEMPLATE_BUILDER` env var /
`--disable-template-builder` flag. When disabled, redirects to old
`/templates/new` flow
- **Registry URL override**: `CODER_TEMPLATE_BUILDER_REGISTRY_URL`
(default: `registry.coder.com`)
- **Requires outbound access** to `registry.coder.com` for `terraform
init` at compose time
- **Modules are bundled** with the Coder release binary; the builder
does not fetch metadata from the registry at runtime
- **Sensitive variables** (secrets) are not collected by the builder;
they are deferred to workspace creation time
- **Module conflicts** show a warning but do not block creation
- **One-way**: No re-entry into the builder for existing templates; edit
HCL directly after creation

## Files to update

### Tier 1: Primary creation flow docs (significant rewrites)

#### 1. `docs/admin/templates/creating-templates.md`

**Current state**: Documents three creation paths: "From a starter
template" (primary), "From an existing template", "From scratch
(advanced)".

**Changes**:
- Add a new section **"Using the template builder"** as the first and
primary section (before "From a starter template").
- Describe the 5-step wizard flow: select base infrastructure, configure
base parameters, select modules, configure module settings, set template
customizations.
- Mention that the builder is enabled by default and requires outbound
access to `registry.coder.com`.
- Note that sensitive variables are collected from developers at
workspace creation, not during template building.
- Add a callout about disabling the builder for airgapped deployments
(`CODER_DISABLE_TEMPLATE_BUILDER`).
- Note the `CODER_TEMPLATE_BUILDER_REGISTRY_URL` option for self-hosted
registry mirrors.
- Keep existing "From a starter template", "From an existing template",
and "From scratch" sections largely intact, but reframe them as
alternative paths.
- Update the "From a starter template" Web UI instructions to note the
new entry point routing (the "New Template" button now goes to the
builder when enabled).
- Fix existing typo: "You can the [Coder CLI]" should be "You can use
the [Coder CLI]".

#### 2. `docs/start/first-template.md`

**Current state**: Beginner tutorial walking through creating a template
from the Docker starter template via the old flow. Has a typo (`s` at
end of line 32), commented-out workspace creation section, and TODO
notes.

**Changes**:
- Rewrite steps 2 and 3 to use the Template Builder as the primary path.
- Step 2: Navigate to **Templates**, select **New Template**, which
opens the Template Builder.
- Step 3: Walk through the builder wizard steps (select Docker base,
optionally select modules like code-server, configure template
name/description, create).
- Remove the typo on line 32 (`s`).
- Keep the "Modify your template" section (step 6) intact since it
covers post-creation editing which is unchanged.
- Remove or update the reference to "Starter Templates" as a separate
page since the builder subsumes that entry point.

#### 3. `docs/get-started/index.md`

**Current state**: Quickstart guide. Step 4 says "Select **Templates** →
**New Template**" then pick "Coder Quickstart" from starter templates.

**Changes**:
- Update Step 4 to describe using the Template Builder.
- The flow becomes: Select **Templates** → **New Template** → builder
opens → select **Coder Quickstart** as the base template → optionally
add modules → set name/description → **Create Template**.
- Update the "What just happened?" explanation to mention the builder
composed and validated the Terraform.
- Screenshot reference `create-quickstart-template.png` will need a new
screenshot (note this in the PR; screenshots are out of scope for this
change but should be flagged).

### Tier 2: Secondary references (targeted edits)

#### 4. `docs/admin/templates/index.md`

**Current state**: Overview page mentioning starter templates as the
primary creation path.

**Changes**:
- Update the "Starter templates" section to mention the Template Builder
as the recommended way to create templates, with starter templates
serving as base templates within the builder.
- Update the link to point to the builder section: `[Create a template
with the template
builder](./creating-templates.md#using-the-template-builder)`.
- Update the screenshot reference and caption. The "Starter Templates"
page screenshot may no longer be the first thing admins see.

#### 5. `docs/admin/templates/managing-templates/index.md`

**Current state**: Documents starter templates, editing, updating,
deleting.

**Changes**:
- Update the "Starter templates" section to mention the Template Builder
as the primary creation path, with starter templates available as base
templates within it.
- Update the image reference from `starter-templates.png` if it shows
the old flow.

#### 6. `docs/tutorials/template-from-scratch.md`

**Current state**: Detailed tutorial for writing a template from scratch
with Terraform.

**Changes**:
- Add a brief note at the top recommending the Template Builder for
users who want to create templates without writing Terraform, with a
link to
`docs/admin/templates/creating-templates.md#using-the-template-builder`.
- In section "7. Create the template in Coder" → "Dashboard" tab, update
the UI steps. The "Upload template" option is now accessed via the old
creation flow at `/templates/new` (or through the "Upload an existing
template" link in the builder's alternatives).
- Fix the inconsistency where text says `coder templates create` but the
code block uses `coder templates push`.

#### 7.
`docs/admin/integrations/devcontainers/envbuilder/add-envbuilder.md`

**Current state**: Documents creating envbuilder templates via
Dashboard, CLI, and Registry tabs.

**Changes**:
- In the Dashboard tab, update the instructions. The "Create Template"
button now opens the builder by default. Users need to use the "Upload
an existing template" alternative link or navigate to `/templates/new`
directly.
- Update "From scratch" reference since that option is now an
alternative link in the builder.
- The CLI and Registry tabs remain unchanged.

#### 8. `docs/install/airgap.md`

**Current state**: Documents air-gapped installations. No mention of
Template Builder.

**Changes**:
- Add a note in the relevant section about the Template Builder
requiring outbound access to `registry.coder.com`.
- Document `CODER_DISABLE_TEMPLATE_BUILDER` for fully air-gapped
deployments.
- Document `CODER_TEMPLATE_BUILDER_REGISTRY_URL` for deployments using a
self-hosted registry mirror.

#### 9. `docs/about/screenshots.md`

**Current state**: Contains a caption "Template administrators can
either create a new Template from scratch or choose a Starter Template".

**Changes**:
- Update the caption to mention the Template Builder as the primary
creation method.
- Screenshot reference may need updating (flag for new screenshot).

### Tier 3: Minor/link-only updates

#### 10. `docs/admin/users/organizations.md`

- If it references the old "Create Template" screen with an org picker,
add a note that the Template Builder also includes organization
selection in its final step.

#### 11. `docs/ai-coder/tasks.md`

- If it mentions creating templates, add a passing reference to the
Template Builder as an option.

## Files NOT to update

- `docs/reference/api/templatebuilder.md`: Auto-generated API reference.
Already correct.
- `docs/reference/api/schemas.md`: Auto-generated. Already correct.
- `docs/reference/cli/server.md`: Auto-generated. Already has
`--disable-template-builder` and `--template-builder-registry-url`.
- `docs/reference/cli/templates_create.md`: Already deprecated.
- `docs/reference/cli/templates.md`: No changes needed.

## Implementation order

1. `docs/admin/templates/creating-templates.md` (primary creation docs,
most content)
2. `docs/get-started/index.md` (quickstart)
3. `docs/start/first-template.md` (beginner tutorial)
4. `docs/admin/templates/index.md` (overview)
5. `docs/admin/templates/managing-templates/index.md` (managing
overview)
6. `docs/install/airgap.md` (airgap note)
7. `docs/tutorials/template-from-scratch.md` (from-scratch tutorial)
8. `docs/admin/integrations/devcontainers/envbuilder/add-envbuilder.md`
(envbuilder)
9. `docs/about/screenshots.md` (screenshot captions)
10. Minor link/reference updates in tier 3 files

## Style notes

- Follow the Diataxis framework; keep tutorials as tutorials, reference
as reference.
- Use present tense, active voice, second person.
- Bold for UI elements: **Templates**, **New Template**, **Create
Template**.
- No emdash/endash.
- Do not add screenshots; flag where new screenshots are needed as
comments/TODOs.
- Run `make fmt/markdown` and `make lint/markdown` after all changes.
- Verify all pages are already in `docs/manifest.json` (no new pages
being added, only existing pages being updated).

</details>

> 🤖 Generated by Coder Agents

docs/get-started/index.md

@@ -215,34 +215,43 @@ lines of output, so you might have to scroll up to find it.
 > [!TIP]
 > If you use an AI coding assistant, the [coder-templates](https://github.com/coder/registry/blob/main/.agents/skills/coder-templates/SKILL.md) agent skill can guide you through creating and customizing templates with best practices built-in.
 
-Templates define what's in your development environment. The following is a basic example:
+Templates define what's in your development environment. The template builder
+guides you through creating one without writing any Terraform.
 
-1. Select **Templates** → **New Template**.
+1. Select **Templates** > **New Template**. The template builder opens.
 
-2. Select the **Coder Quickstart** template from the list of starter templates.
+1. Select the **Docker** base template from the list.
 
-   **Note:** running this template requires Docker to be running in the background, so make sure Docker is running!
+   > [!NOTE]
+   > This template requires Docker to be running in the background, so make sure Docker is running.
 
-3. Name your template.
-   The **Display name** and **Description** are pre-filled from the starter template, so you can keep the defaults or replace them:
-   - **Name**: `quickstart`
-   - **Display name**: `Coder Quickstart`
-   - **Description**: `Get started with Coder by picking your languages, editors, and a repo`
+1. Skip or configure any base template parameters, then select modules to add
+   IDEs and tools to your template. For example, add **code-server** to get
+   VS Code in the browser. You can skip module selection for now and add
+   modules later.
 
-4. Select **Save**.
+1. On the final step, name your template:
+   - **Name**: `my-docker-template`
+   - **Display name** and **Description**: fill in as you like.
 
-   ![Create template](../images/screenshots/create-quickstart-template.png)
+1. Select **Create Template**. Coder composes and validates the Terraform
+   configuration, then creates your template.
+
+   ![Template builder base selection step](../images/templatebuilder_01_bases.png)
 
 **What just happened?**
-You defined a template, a reusable blueprint for dev environments, in your Coder deployment.
-It's now stored in your organization's template list, where you and any teammates in the same organization can create workspaces from it.
+The template builder selected a base infrastructure template, composed it with
+any modules you chose, and generated a valid Terraform configuration. Coder
+validated the configuration server-side, then created a reusable template in
+your organization's template list. You and any teammates in the same
+organization can now create workspaces from it.
 
 <details>
 <summary>What happens under the hood?</summary>
 
 A Coder template is a [Terraform](https://developer.hashicorp.com/terraform/intro) configuration, and Coder is built on top of Terraform.
 When you create a workspace from this template, a Coder [provisioner](../admin/infrastructure/architecture.md#provisionerd) runs a Terraform job from the template's configuration to build your environment.
-For the Coder Quickstart template, that job starts a Docker container, connects the Coder agent, and runs a startup script that installs the programming languages and editors you choose in the next step.
+For the Docker base template, that job starts a Docker container with the Coder agent pre-configured, along with any modules you selected.
 
 To learn how Coder uses Terraform to provision and run workspaces, refer to the [architecture overview](../admin/infrastructure/architecture.md).
 
@@ -254,19 +263,15 @@ Now it's time to launch a workspace.
 
 1. After the template is ready, select **+ Create Workspace**.
 
-2. Give the workspace a name. If you need a suggestion for a workspace, you can select the automatically generated name next to the **Need a suggestion?** label.
+1. Give the workspace a name. If you need a suggestion, you can select the
+   automatically generated name next to the **Need a suggestion?** label.
 
-3. In this window are [parameters](../admin/templates/extending-templates/parameters.md) that customize the workspace's behavior. Set the following based on your needs:
+1. If the template has any
+   [parameters](../admin/templates/extending-templates/parameters.md), fill
+   them in. Parameters vary by template and the modules you selected in the
+   builder.
 
-   - **Programming Languages**: the languages to pre-install in your workspace. You can use more than one if you want.
-   - **IDEs & Editors**: the IDEs and editors you want to configure for quick access once the workspace is running. You can choose more than one if you want.
-   - **Git Repository (Optional)**: the Git repository you want to clone into your workspace. Leave this field blank to skip it.
-
-   **Note:** If you use any of the JetBrains IDEs as your preferred IDE (such as PyCharm, GoLand, or RustRover), select **JetBrains IDEs** as the value. A new parameter will appear, with which you can choose your preferred JetBrains IDE.
-
-     ![Workspace creation screen](../images/screenshots/create-workspace.png)_Workspace creation screen_
-
-4. Launch your workspace by selecting **Create workspace**.
+1. Select **Create workspace**.
 
 After a short wait (10-15 seconds on most modern computers), Coder will start your new workspace:
 
@@ -275,7 +280,7 @@ After a short wait (10-15 seconds on most modern computers), Coder will start yo
 ## Step 6: Connect your IDE
 
 Each button in the workspace view is a different **agent app**.
-The buttons you see reflect the editors you selected in the **IDEs & Editors** parameter in [Step 5](#step-5-launch-your-workspace).
+The buttons in the UI reflect the modules you added in the template builder (such as code-server, Claude Code, or any of the JetBrains editors).
 Select your preferred IDE from the list of agent apps.
 
 This guide uses **VS Code Desktop**, which opens the workspace in the VS Code installed on your local machine, using the Coder extension.