chore: add lefthook pre-commit hooks

[lanesawyer]

What

Add lefthook pre-commit hooks. The hook autofixes what it can on commit and never blocks — CI remains the gate for anything unfixable.

📚 Stacked on #289 (pnpm 11 upgrade). Hook installation relies on allowBuilds in pnpm-workspace.yaml, which is pnpm 11 syntax, so this must merge after #289. Review the diff against lane/upgrade-pnpm-11.

How

Adds lefthook.yml with three pre-commit commands:

Command	Files	Tool
lint	JS/TS + .astro	oxlint --fix
fmt	JS/TS/JSON/YAML/MD/MDX/HTML	oxfmt
fmt-astro	.astro	prettier --write

Plus a lefthook devDependency and lefthook: true under allowBuilds in pnpm-workspace.yaml.

Notable details:

• Non-blocking. Each command ends in || true, so an unfixable lint error is printed but still lets the commit through.
• stage_fixed: true re-stages files the tools modified, so the commit records the formatted output rather than what was originally staged.
• priority forces oxlint --fix to run before oxfmt. Lefthook orders commands alphabetically by default, which would have run the formatter first and left lint autofixes unformatted.
• glob per command must cover every file type its tool handles. The globs were derived by probing the tools rather than assuming: oxfmt reformats js/jsx/mjs/cjs/mts/cts/ts/tsx/json/jsonc/yaml/yml/md/mdx/html, and oxlint reads .astro in addition to JS/TS. An earlier revision omitted md/mdx/html/astro, which let a markdown- or astro-only commit skip the hook and then fail CI.
• Hook installation follows lefthook's documented pnpm setup — allow its postinstall to run, and that syncs the hooks. Note the docs also say to add pnpm.onlyBuiltDependencies to package.json; pnpm 11 ignores that field and warns about it, so only the pnpm-workspace.yaml entry is used.

Verification

Tested from fresh clones on pnpm 11.21.0, driving real git commit calls and asserting on committed blob contents:

• Fresh clone → pnpm install → pre-commit hook present; a badly formatted .ts then commits as formatted output.
• A .ts with an unfixable no-console error plus bad formatting: commit succeeds, error reported, committed blob is formatted.
• An unformatted .md makes pnpm run check exit 1; the hook formats and re-stages it, so CI stays green.
• An .astro file with a lint error is reported by oxlint and formatted by prettier.
• Staging only a file no tool handles: all three commands skip, zero files touched.

PR Checklist

• Is your PR title following our conventional commit naming recommendations?
• Have you filled in the PR Description Template?
• Is your branch up to date with the latest in main?
• Do the CI checks pass successfully? (Lint fails by design until the demo console.log is removed)
• Have you smoke tested the example applications?
• Did you check that the changes meet accessibility standards?
• Have you tested the application on these browsers?
  • Chrome (Fully supported)
  • Firefox (Major bug fixes supported)
  • Safari (Major bug fixes supported)

[lanesawyer]

I made a trivial spacing change on this file to see if it would run it on the staged file and it did!! Woooo!

[froyo-np]

So I disable husky pre-hook stuff locally - it does not play nice with git on windows. I'm agreeable to adding this, but I'd really really like to remove some (most?) of these lint rules.

[lanesawyer]

Sorry, could've made the intent here clearer. This is to auto-fix any fixable rules or formatting on commit, not to block commits if they fail a check.

Also I need to verify it's working how I expect! I forgot to test if it allows you to successfully commit with a linting error in the code.

[lanesawyer]

Shoot, it does prevent commits if there are errors. Will look into this again later!

[lanesawyer]

Finally got back to this and made it so it doesn't block any commits if there are lint errors happening while still doing any formatting or safe linting fixes! This is ready to go 😁