Normalize 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:

- tf, terraform -> hcl
- pwsh -> powershell
- env, output -> text
- Dockerfile -> dockerfile

promql fences are left as-is; Shiki doesn't bundle a promql grammar,
so it needs a custom grammar registration when the site adopts Shiki
(DOCS-118), rather than degrading to text.

Updates the formatting style guide to document the canonical tags.

DOCS-476

Correcting the normalization from the previous commit:

- tf and hcl both mapped to hcl, but Shiki ships terraform and hcl as
  two distinct grammars (Terraform's own resource/provider syntax vs
  generic HCL used by other HashiCorp tools like Vault). Nearly every
  fenced block in docs/** is literal Terraform code, so terraform is
  the correct canonical tag, not hcl.
- env mapped to text, discarding real syntax highlighting, but Shiki
  bundles a dedicated dotenv grammar for exactly this KEY=VALUE
  content, so env blocks now map to dotenv instead.

Verified every fence tag now used under docs/** against the full list
of Shiki's 235 bundled languages and aliases (only promql remains
unsupported, as already documented).

DOCS-476

- Revert the canonical Terraform/HCL fence tag from Usage: terraform [global options] <subcommand> [args]

The available commands for execution are listed below.
The primary workflow commands are given first, followed by
less common or more advanced commands.

Main commands:
  init          Prepare your working directory for other commands
  validate      Check whether the configuration is valid
  plan          Show changes required by the current configuration
  apply         Create or update infrastructure
  destroy       Destroy previously-created infrastructure

All other commands:
  console       Try Terraform expressions at an interactive command prompt
  fmt           Reformat your configuration in the standard style
  force-unlock  Release a stuck lock on the current workspace
  get           Install or upgrade remote Terraform modules
  graph         Generate a Graphviz graph of the steps in an operation
  import        Associate existing infrastructure with a Terraform resource
  login         Obtain and save credentials for a remote host
  logout        Remove locally-stored credentials for a remote host
  metadata      Metadata related commands
  modules       Show all declared modules in a working directory
  output        Show output values from your root module
  providers     Show the providers required for this configuration
  query         Search and list remote infrastructure with Terraform
  refresh       Update the state to match remote systems
  show          Show the current state or a saved plan
  stacks        Manage HCP Terraform stack operations
  state         Advanced state management
  taint         Mark a resource instance as not fully functional
  test          Execute integration tests for Terraform modules
  untaint       Remove the 'tainted' state from a resource instance
  version       Show the current Terraform version
  workspace     Workspace management

Global options (use these before the subcommand, if any):
  -chdir=DIR    Switch to a different working directory before executing the
                given subcommand.
  -help         Show this help output or the help for a specified subcommand.
  -version      An alias for the "version" subcommand. to :
  both resolve to the same, correct grammar (Shiki's terraform grammar
  bundles tf/tfvars as aliases; GitHub's starry-night renderer matches
  tf via its HCL grammar's file extensions), so there's no functional
  difference, and tf is shorter to type.
- Normalize indented fence tags (nested inside numbered/bulleted lists)
  that the original column-0-only sed pass never touched: hcl/terraform
  -> tf, env -> dotenv, output/none/url -> text, Dockerfile -> dockerfile,
  across ~20 additional files.
- Document that caddyfile (2 fences in reverse-proxy-caddy.md) is, like
  promql, a grammar Shiki doesn't bundle and stays as-is pending a
  custom grammar registration.

- text -> txt for command output / no-highlight blocks. Both are
  Shiki's built-in plain-text fallback (txt/plain are explicit aliases
  of text, neither uses a real grammar), and GitHub's starry-night
  renderer doesn't recognize either as a language, so both already
  render unhighlighted there today. No functional difference; txt is
  shorter.
- powershell -> ps1. Confirmed via shiki.bundledLanguagesInfo that ps1
  is a registered PowerShell alias in Shiki. On GitHub's starry-night,
  the PowerShell grammar's extensions list includes .ps1 (not bare
  .ps), and flagToScope() falls back to extension matching when a flag
  isn't a recognized language name, so ps1 resolves to the same
  highlighting as powershell there too. ps does not: it's neither a
  registered name nor a registered extension, so it would silently
  render unhighlighted on GitHub today.
- Updated docs/.style/style-guide/formatting.md accordingly.

…to tsx, yml to yaml

- bash, shell -> sh (732 fences). Shiki bundles bash/sh/shell/zsh as
  aliases of a single shellscript grammar; GitHub's starry-night shell
  grammar likewise treats all three as names for source.shell. Applies
  the style guide's existing (but previously unenforced) sh preference
  across the whole corpus.
- markdown -> md (4 fences). Shiki's markdown grammar has md as an
  explicit alias; GitHub's markdown grammar likewise lists md among its
  names.
- jsonc -> json (1 fence, docs/ai-coder/ai-gateway/clients/mux.md). The
  block has no comments or trailing commas, so it doesn't need the
  JSON-with-comments grammar; jsonc stays reserved for blocks that
  actually use it.
- ts -> tsx (2 fences, docs/about/contributing/frontend.md). Verified
  the actual content tokenizes identically under both grammars (no
  legacy angle-bracket type-assertion syntax present), and one sibling
  block in the same file already needs tsx for real JSX, so tsx is safe
  as the single tag for that file's TypeScript blocks.
- yml -> yaml (1 fence). Shiki and GitHub both alias yml to yaml.
- Updated docs/.style/style-guide/formatting.md with the new canonical
  tags, including a note on tsx's legacy-cast-syntax caveat and on
  jsonc's narrower scope.

The earlier normalization sweeps only touched checked-in docs/**
output, not the generator sources. A future 'make gen' would have
reverted docs/reference/api/*.md fences back to 'shell' since the
widdershins --language_tabs flag and postprocess/main.go template
still emitted the old tag.

widdershins loads a user-template file named code_${language_tab}.dot
to render each language tab's code sample, so renaming the shell tab
to 'sh' required renaming code_shell.dot to code_sh.dot as well;
otherwise widdershins silently drops the '### Code samples' curl
block for every endpoint (verified by regenerating and diffing).

- generate.sh: --language_tabs "shell:curl" -> "sh:curl"
- markdown-template/code_shell.dot -> code_sh.dot (renamed to match)
- security.def: shell -> sh for the 'coder tokens create' example
- postprocess/main.go: shell -> txt (bare URL, no shell syntax) and
  shell -> sh (real curl command) in the apiIndexContent template
- docs/reference/api/index.md: synced checked-in output to match

Verified by running 'rm coderd/apidoc/.gen && make coderd/apidoc/.gen'
end to end: regenerated output is now byte-identical to the checked-in
docs/reference/api/*.md files.