ci: add lint and format check job, update CONTRIBUTING.md

[vanceingalls]

Summary

• Add lint-and-format job to CI workflow (pnpm lint + pnpm format:check)
• Fix lefthook commands to use npx prefix (bare binaries not on PATH)
• Update CONTRIBUTING.md: document new tooling, commit conventions, and lefthook hooks

Part 4/4 of VA-851

Test plan

• CI job matches existing pattern (pnpm 10, node 22, frozen lockfile)
• Git hooks work end-to-end (bad messages rejected, valid commits pass)
• CONTRIBUTING.md accurately reflects new tooling

[linear]

VA-851 [Pre-Migration] Configure ESLint, Prettier, and conventional commits

Context

The codebase currently has no linting or formatting enforcement. Code is clean by convention, but OSS contributors need automated guardrails. Team feedback: "I love when an open source repo has this."

What to do

1. ESLint — add configuration at monorepo root with TypeScript rules. Extend from @typescript-eslint/recommended.
2. Prettier — add .prettierrc at root. Configure for the existing code style (double quotes, no semicolons or with — match what's already there).
3. Conventional commits — add commitlint config enforcing conventional commit format (feat:, fix:, refactor:, etc.). This enables automated changelog generation later.
4. Run formatter across all source files to establish baseline (single "format" commit in internal repo before port).
5. Add lint/format scripts to root package.json: pnpm lint, pnpm format, pnpm format:check
6. Verify all existing code passes lint + format checks with zero errors

Why before port

We want the OSS repo's first commit to already have these configs in place and all code conforming. No "fix linting" commits in public history.

[vanceingalls]

• perf: replace tsc with tsgo for ~3x faster type checking #29
• build: migrate from pnpm to bun as package manager #28
• ci: add lint and format check job, update CONTRIBUTING.md #26 👈 (View in Graphite)
• style: apply oxfmt baseline formatting across all source files #25
• fix: resolve oxlint errors across codebase #24
• build: add oxlint, oxfmt, commitlint, lefthook, knip, and editorconfig configs #23
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[vanceingalls]

Merge activity

• Mar 24, 1:49 AM UTC: @vanceingalls merged this pull request with Graphite.