build: switch project to pnpm

[kunchenguid]

What Changed

• Replaced npm package management with pnpm via packageManager, pnpm-lock.yaml, and pnpm-workspace.yaml, removing package-lock.json.
• Updated CI, release, and airlock lint workflows to install with pnpm install --frozen-lockfile and run tooling through pnpm.
• Updated contributor documentation for pnpm commands and added coverage for the airlock lint helper behavior.

Risk Assessment

✅ Low: The changes are narrowly scoped to switching install, CI, and lint helper commands from npm/npx to pnpm, with the prior npm fallback issue addressed and no material new risks found.

Testing

• Summary: Exercised pnpm lockfile installation and the full Vitest suite for the pnpm migration; all completed successfully.
• pnpm install --frozen-lockfile
• pnpm test
• Outcome: ✅ passed across 1 run (59.9s)

Pipeline

Updates from git push no-mistakes

⏭️ **intent** - skipped

Round 1 - passed ✅

✅ **Rebase** - passed

Round 1 - passed ✅

🔧 **Review** - 1 issue found → auto-fixed

Round 1 - found 1 warning

• ⚠️ package.json:4 - Switching the repository to pnpm leaves the no-mistakes lint helper on its npm fallback path when dependencies are missing, so clean local/gate runs for future TypeScript changes can ignore pnpm-lock.yaml and the pnpm workspace supply-chain settings by running npm install --ignore-scripts; update that helper to install with pnpm or remove the npm fallback.

Round 2 (auto-fix) - passed ✅

✅ **Test** - passed

Round 1 - passed ✅

• pnpm install --frozen-lockfile
• pnpm test

🔧 **Document** - 2 issues found → auto-fixed

Round 1 - found 2 warnings

• ⚠️ README.md:226 - The change switches the project development workflow from npm/npx to pnpm by adding packageManager "pnpm@11.1.1", replacing package-lock.json with pnpm-lock.yaml, updating CI/release installs to pnpm install --frozen-lockfile, and changing the airlock lint script to use pnpm exec. The README Development section still documents npm run build, npm run dev, npm test, and npm run test:watch, and the Session Hooks note still names npm run dev as the development entrypoint. Update these developer commands to the pnpm equivalents so contributors follow the new package manager.
• ⚠️ CONTRIBUTING.md:36 - The repository conventions still instruct contributors to run npm run build and npm test before pushing, but this branch changes CI and local tooling to pnpm with a pnpm lockfile and packageManager declaration. Update the pre-push commands to pnpm run build and pnpm test, and consider noting pnpm as the required package manager in the repo conventions.

Round 2 (auto-fix) - passed ✅

🔧 **Lint** - 2 issues found → auto-fixed

Round 1 - found 2 warnings

• ⚠️ README.md:1 - Prettier reported code style issues in this changed Markdown file. Run pnpm exec prettier --write README.md to normalize formatting.
• ⚠️ pnpm-lock.yaml:1 - Prettier reported code style issues in this changed YAML lockfile. Run pnpm exec prettier --write pnpm-lock.yaml to normalize formatting.

Round 2 (auto-fix) - passed ✅

✅ **Push** - passed

Round 1 - passed ✅