feat(formatters): add stylua, nimpretty, and elm-format formatters

[sahitya-chandra]

Issue for this PR

Closes #XXXX

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

Adds built-in formatter support for Lua, Nim, and Elm

Changes

• packages/opencode/src/format/formatter.ts

  • stylua – Lua (.lua), enabled when stylua is on PATH
  • nimpretty – Nim (.nim), enabled when nimpretty is on PATH, command: nimpretty -w $FILE
  • elm-format – Elm (.elm), enabled when elm-format is on PATH, command: elm-format --yes $FILE

• packages/web/src/content/docs/formatters.mdx

  • Documented the three new formatters in the built-in formatters table (extensions and requirements).

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How did you verify your code works?

The code was verified with typecheck + lint only. No automated or manual runtime verification was done, but I made sure that it follows the same code pattern as other existing formatters

Screenshots / recordings

If this is a UI change, please include a screenshot or recording.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

If you do not follow this template your PR will be automatically rejected.

[github-actions]

Hey! Your PR title Add stylua, nimpretty, and elm-format formatters doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential Duplicate Found

PR #14855 - "feat(opencode): add stylua formatter support for Lua files"
#14855

Why it's related: This PR specifically adds stylua formatter support for Lua files, which is one of the three formatters being added in the current PR #17618. This appears to be a partial implementation that may overlap with the new PR's scope.

[github-actions]

Thanks for updating your PR! It now meets our contributing guidelines. 👍