ci: add auto-publish workflow for npm releases on version bump

[jlucus]

Summary

Adds GitHub Actions workflow for automatic npm publishing when version bumps are merged to main via changesets.

Changes

New Workflow: .github/workflows/publish.yml

Trigger: Version bump on main (when package.json or CHANGELOG.md change)

Pipeline:

1. Checkout code
2. Setup Node.js 20
3. Install dependencies
4. Build package (npm run build)
5. Type checking (npm run typecheck)
6. Run benchmarks (npm run benchmark)
7. Publish to npm (using NPM_TOKEN secret)
8. Create GitHub Release with changelog

How It Works

Developer Flow

# 1. Developer creates changeset
npm run changeset:add

# 2. Maintainer bumps version
npm run release:version

# 3. Push to main → Automatic npm publish!
git push origin main

CI/CD Automation

• Detects version bump from changesets
• Runs all pre-publish checks
• Publishes to npm registry
• Creates GitHub Release automatically
• No manual steps needed

Requirements

• ✅ NPM_TOKEN secret configured (expires Nov 27, 2026)
• ✅ Changesets configured for versioning
• ✅ CHANGELOG automation ready

Benefits

• 🚀 Hands-off publishing
• ✅ Consistent build checks before publish
• 🏷️ Automatic GitHub Releases
• 📊 Benchmarks run on every release
• 🔒 Uses secrets for authentication

Testing

To verify the workflow:

1. Create changeset: npm run changeset:add
2. Version bump: npm run release:version
3. Push to main (or merge to main)
4. Watch GitHub Actions run the publish workflow

Notes

• Workflow only triggers if package.json changes (indicates version bump)
• Requires successful build, typecheck, and benchmark to publish
• GitHub Release created with full changelog
• Failed checks block publishing (quality gate)

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