docs: normalize code-fence languages for Shiki compatibility (#27161)

Normalizes non-standard code-fence language tags across `docs/**` so a
strict highlighter (Shiki, used by Fumadocs) won't fail the build on an
unrecognized language, and unifies redundant synonym tags onto one
canonical form per language. The current renderer (Speed-Highlight)
detects the language from the code content, not the fence label, so this
drift wasn't visible until now.

## Changes

- `hcl` -> `tf` (199 fences, including indented ones nested in
numbered/bulleted lists). Shiki ships `hcl` and `terraform` as two
distinct grammars (not aliases); every `hcl`-tagged fence in `docs/**`
is actually Terraform resource/data/provider syntax, so the more
specific `terraform` grammar is correct for all of them. `tf` is Shiki's
own alias for that grammar, and it's also what GitHub's own markdown
renderer resolves to the same HCL/Terraform highlighting.
- `pwsh`/`powershell` -> `ps1`. Both `ps` and `ps1` are registered
PowerShell aliases in Shiki, but on GitHub's renderer only `.ps1` is a
registered file extension (`.ps` isn't), so `ps1` renders identically to
`powershell` there today while bare `ps` would silently lose
highlighting.
- `env` -> `dotenv` (a dedicated Shiki grammar for `KEY=VALUE` files)
- `text`/`output`/`none`/`url` -> `txt`. Same built-in plain-text
fallback either way, just shorter.
- `Dockerfile` -> `dockerfile` (lowercase)
- `bash`/`shell` -> `sh` (732 fences). Shiki and GitHub both alias all
three to a single shell grammar; this was already the style guide's
stated preference, just not enforced across the existing corpus until
now.
- `markdown` -> `md` (4 fences). Alias of the same grammar in both Shiki
and GitHub.
- `jsonc` -> `json` (1 fence). The block has no comments or trailing
commas, so it doesn't need the comments-capable grammar.
- `ts` -> `tsx` (2 fences, `docs/about/contributing/frontend.md`).
Verified the actual content tokenizes identically under both grammars,
and a sibling block in the same file already needs `tsx` for real JSX,
so unifying to one tag is safe for this file. Documented a caveat: `tsx`
mis-tokenizes the legacy angle-bracket type-assertion syntax
(`<Type>value`), which is invalid in real `.tsx` files anyway, so use
`value as Type` instead.
- `yml` -> `yaml` (1 fence)
- Updated `docs/.style/style-guide/formatting.md` to document all
canonical tags

`promql` (2 fences) and `caddyfile` (2 fences) are left as-is. Shiki
doesn't bundle a grammar for either, so they need a custom grammar
registration when the site adopts Shiki, rather than degrading to `txt`.
Tracked as follow-up work under DOCS-118 and
[DOCS-544](https://linear.app/codercom/issue/DOCS-544/vendor-a-local-promql-grammar-for-shiki-syntax-highlighting)
(promql).

Does not touch `offlinedocs/`.

Linear:
[DOCS-476](https://linear.app/codercom/issue/DOCS-476/normalize-docs-code-fence-languages-de-risk-shikifumadocs)

<details>
<summary>How the fence tags were verified</summary>

Each tag was tested against a real `shiki@latest` highlighter instance
(`codeToHtml`/`codeToTokens`) and cross-checked against GitHub's
`@wooorm/starry-night` grammar sources (the renderer that actually
displays these `.md` files today, in repo browsing and PR diffs), since
that's what determines whether brevity is safe before Shiki adoption:

```text
FAIL  env        -- Language `env` is not included in this bundle.
FAIL  Dockerfile -- Language `Dockerfile` is not included in this bundle.
FAIL  promql     -- Language `promql` is not included in this bundle.
FAIL  caddyfile  -- Language `caddyfile` is not included in this bundle.
FAIL  pwsh       -- Language `pwsh` is not included in this bundle.
FAIL  output     -- Language `output` is not included in this bundle.
```

`hcl` doesn't error in Shiki, since it's a real grammar, but that's
exactly the trap: it was silently rendering every fence with the generic
HCL grammar instead of the Terraform-specific one. Every `hcl`-tagged
fence in `docs/**` was manually checked against `origin/main` and is
genuinely Terraform content.

For `ts`/`tsx`, tokenizing the actual doc content confirmed identical
output under both grammars; a synthetic test with the legacy
angle-bracket cast syntax confirmed `tsx` degrades on that specific
construct, which the style guide now calls out.

The first normalization pass only matched fence tags at column 0
(`^```tag$`), missing tags indented inside numbered/bulleted lists. A
follow-up pass caught the remaining occurrences at any indentation
level.

</details>


---

*This PR description and the underlying changes were prepared with Coder
Agents assistance.*

docs/admin/integrations/devcontainers/envbuilder/add-envbuilder.md

@@ -25,7 +25,7 @@ choose a template from the
 
 1. Use the `template init` command to initialize your choice of image:
 
-   ```shell
+   ```sh
    coder template init --id kubernetes-devcontainer
    ```
 
@@ -34,7 +34,7 @@ choose a template from the
 
 1. `cd` into the directory and push the template to your Coder deployment:
 
-   ```shell
+   ```sh
    cd kubernetes-devcontainer && coder templates push
    ```
 
@@ -52,7 +52,7 @@ choose a template from the
 
    - CLI:
 
-   ```shell
+   ```sh
    coder templates push <template-name> -d <path to folder containing main.tf>
    ```
 
@@ -65,7 +65,7 @@ choose a template from the
 
       - To zip the files through the command line:
 
-        ```shell
+        ```sh
         zip templates.zip Dockerfile main.tf
         ```
 

docs/admin/integrations/devcontainers/integration.md

@@ -40,7 +40,7 @@ Use the
 [devcontainers-cli](https://registry.coder.com/modules/devcontainers-cli) module
 to ensure the `@devcontainers/cli` is installed in your workspace:
 
-```terraform
+```tf
 module "devcontainers-cli" {
   count    = data.coder_workspace.me.start_count
   source   = "registry.coder.com/coder/devcontainers-cli/coder"
@@ -57,7 +57,7 @@ The
 resource automatically starts a Dev Container in your workspace, ensuring it's
 ready when you access the workspace:
 
-```terraform
+```tf
 resource "coder_devcontainer" "my-repository" {
   count            = data.coder_workspace.me.start_count
   agent_id         = coder_agent.dev.id
@@ -83,7 +83,7 @@ default behavior.
 If you need to explicitly disable Dev Containers, set the
 `CODER_AGENT_DEVCONTAINERS_ENABLE` environment variable to `false`:
 
-```terraform
+```tf
 resource "docker_container" "workspace" {
   count = data.coder_workspace.me.start_count
   image = "codercom/oss-dogfood:latest"
@@ -153,7 +153,7 @@ and [`coder_env`](https://registry.terraform.io/providers/coder/coder/latest/doc
 resources to a `coder_devcontainer` by referencing its `subagent_id` attribute
 as the `agent_id`:
 
-```terraform
+```tf
 resource "coder_devcontainer" "my-repository" {
   count            = data.coder_workspace.me.start_count
   agent_id         = coder_agent.dev.id
@@ -227,7 +227,7 @@ For the full reference, see
 Here's a simplified template example that uses Dev Containers with manual
 configuration:
 
-```terraform
+```tf
 terraform {
   required_providers {
     coder  = { source = "coder/coder" }
@@ -277,7 +277,7 @@ resource "coder_env" "env" {
 By default, discovered containers appear in the dashboard but developers must
 manually start them. To have them start automatically, enable autostart:
 
-```terraform
+```tf
 resource "docker_container" "workspace" {
   count = data.coder_workspace.me.start_count
   image = "codercom/oss-dogfood:latest"