feat: add Quickstart template with language and IDE selection (#24904)

Add a new Quickstart starter template that lets users pick programming
languages, editors, and an optional Git repo to clone. The template uses
Docker under the hood but presents a developer-focused experience: pick
your tools, start coding.

## What's included

- **Languages parameter** (multi-select): Python, Node.js, Go, Rust,
Java, C/C++
- **IDEs parameter** (multi-select): VS Code (Browser), VS Code Desktop,
Cursor, JetBrains, Zed, Windsurf
- **Git repo parameter**: Optional URL to clone on workspace start
- **JetBrains filtering**: Maps selected languages to relevant IDE codes
(Python → PyCharm, Go → GoLand, etc.)
- **Docker precondition check**: Uses `data "external"` +
`terraform_data` precondition to surface a friendly error when Docker is
unavailable, before the Docker provider fails with a cryptic message
- **4 presets**: Web Development, Backend (Go), Data Science, Full Stack
- **Single install script**: All languages install in one `coder_script`
to avoid apt-get lock conflicts (agent scripts run in parallel via
`errgroup`)

<details><summary>Design decisions</summary>

- **Docker as invisible backend**: Docker is required on the Coder
server but never mentioned in the user-facing parameter UI. The
experience is entirely "pick languages, pick editors, start coding."
- **`coder_script` over startup_script**: Language installs use a
templated script file (`install-languages.sh.tftpl`) driven by the
languages parameter. A single script avoids dpkg lock contention since
`coder_script` resources execute concurrently.
- **`data "external"` for Docker check**: The external provider probes
Docker availability independently of the Docker provider. If Docker is
down, the `terraform_data` precondition fails with a human-readable
message before any `docker_*` resource is evaluated. This depends on the
Docker provider connecting lazily (at resource eval time, not at
provider init), which current behavior confirms.
- **JetBrains filtering by language**: Rather than showing all 9
JetBrains IDEs, the template computes relevant IDE codes from the
language selection (e.g. Python → PY, Go → GO) and passes them as
`default` to the JetBrains module.
- **Arch-aware Go install**: The install script detects `uname -m` to
download the correct Go binary for amd64 or arm64.

</details>

<details><summary>Screenshots and recordings from the UI</summary>
<p>
<img width="1851" height="1471" alt="Screenshot 2026-05-05 at 2 14
20 PM"
src="https://github.com/user-attachments/assets/d4c9cdc5-d311-43a5-9e2e-f90b0019eda7"
/>
<img width="1851" height="1471" alt="Screenshot 2026-05-05 at 2 15
06 PM"
src="https://github.com/user-attachments/assets/cf3023fe-b6db-4503-a6c4-eaa0ec0659f8"
/>


https://github.com/user-attachments/assets/7507fd7d-ddb5-457a-9f7d-cbf89b36eb20


</p>
</details> 

> [!NOTE]
> This PR was authored by Coder Agents.

examples/examples.gen.json

@@ -210,6 +210,18 @@
 		],
 		"markdown": "\n# Remote Development on Nomad\n\nProvision Nomad Jobs as [Coder workspaces](https://coder.com/docs/workspaces) with this example template. This example shows how to use Nomad service tasks to be used as a development environment using docker and host csi volumes.\n\n\u003c!-- TODO: Add screenshot --\u003e\n\n\u003e **Note**\n\u003e This template is designed to be a starting point! Edit the Terraform to extend the template to support your use case.\n\n## Prerequisites\n\n- [Nomad](https://www.nomadproject.io/downloads)\n- [Docker](https://docs.docker.com/get-docker/)\n\n## Setup\n\n### 1. Start the CSI Host Volume Plugin\n\nThe CSI Host Volume plugin is used to mount host volumes into Nomad tasks. This is useful for development environments where you want to mount persistent volumes into your container workspace.\n\n1. Login to the Nomad server using SSH.\n\n2. Append the following stanza to your Nomad server configuration file and restart the nomad service.\n\n   ```tf\n   plugin \"docker\" {\n     config {\n       allow_privileged = true\n     }\n   }\n   ```\n\n   ```shell\n   sudo systemctl restart nomad\n   ```\n\n3. Create a file `hostpath.nomad` with following content:\n\n   ```tf\n   job \"hostpath-csi-plugin\" {\n     datacenters = [\"dc1\"]\n     type = \"system\"\n\n     group \"csi\" {\n       task \"plugin\" {\n         driver = \"docker\"\n\n         config {\n           image = \"registry.k8s.io/sig-storage/hostpathplugin:v1.10.0\"\n\n           args = [\n             \"--drivername=csi-hostpath\",\n             \"--v=5\",\n             \"--endpoint=${CSI_ENDPOINT}\",\n             \"--nodeid=node-${NOMAD_ALLOC_INDEX}\",\n           ]\n\n           privileged = true\n         }\n\n         csi_plugin {\n           id   = \"hostpath\"\n           type = \"monolith\"\n           mount_dir = \"/csi\"\n         }\n\n         resources {\n           cpu    = 256\n           memory = 128\n         }\n       }\n     }\n   }\n   ```\n\n4. Run the job:\n\n   ```shell\n   nomad job run hostpath.nomad\n   ```\n\n### 2. Setup the Nomad Template\n\n1. Create the template by running the following command:\n\n   ```shell\n   coder template init nomad-docker\n   cd nomad-docker\n   coder template push\n   ```\n\n2. Set up Nomad server address and optional authentication:\n\n3. Create a new workspace and start developing.\n"
 	},
+	{
+		"id": "quickstart",
+		"url": "",
+		"name": "Coder Quickstart",
+		"description": "Get started with Coder by picking your languages, editors, and a repo",
+		"icon": "/icon/coder.svg",
+		"tags": [
+			"docker",
+			"quickstart"
+		],
+		"markdown": "\n# Coder Quickstart\n\nGet up and running with Coder in minutes. Choose your programming languages, pick your preferred editors, optionally clone a Git repository, and start coding.\n\n## How It Works\n\nWhen you create a workspace from this template, you select:\n\n1. **Languages** to pre-install (Python, Node.js, Go, Rust, Java, C/C++)\n2. **Editors** to connect (VS Code in the browser, VS Code Desktop, Cursor, JetBrains, Zed, Windsurf)\n3. **A Git repository** to clone (optional)\n\nCoder provisions a workspace with your selections and you can start developing immediately.\n\n## Prerequisites\n\nThe host running Coder must have a Docker daemon accessible to the `coder` user:\n\n```sh\n# Add coder user to Docker group\nsudo adduser coder docker\n\n# Restart Coder server\nsudo systemctl restart coder\n\n# Verify access\nsudo -u coder docker ps\n```\n\n## Architecture\n\nThis template provisions:\n\n- **Docker container** (ephemeral) running Ubuntu with the Coder agent\n- **Docker volume** (persistent) mounted at `/home/coder`\n\nFiles in your home directory persist across workspace restarts. Selected languages are installed on first start and cached for subsequent starts.\n\n## Presets\n\nSelect a preset to auto-fill languages and editors for common workflows:\n\n| Preset              | Languages           | Editors                             |\n|---------------------|---------------------|-------------------------------------|\n| **Web Development** | Python, Node.js     | VS Code (Browser)                   |\n| **Backend (Go)**    | Go                  | VS Code (Browser), JetBrains GoLand |\n| **Data Science**    | Python              | VS Code (Browser)                   |\n| **Full Stack**      | Python, Node.js, Go | VS Code (Browser), Cursor           |\n\n## IDE Notes\n\n- **VS Code (Browser)**: Opens directly in your browser with no local install required.\n- **VS Code Desktop, Cursor, Windsurf**: Require the desktop application installed on your local machine. Coder opens them via protocol handler.\n- **JetBrains IDEs**: Filtered by your language selection (e.g. PyCharm for Python, GoLand for Go). Requires JetBrains Toolbox or Gateway on your local machine.\n- **Zed**: Connects over SSH. Requires Zed installed on your local machine.\n"
+	},
 	{
 		"id": "scratch",
 		"url": "",