feat: add tag-triggered release workflow

[purupurupu]

Summary

• Add .github/workflows/release.yml triggered on v* tag push
• Runs full CI checks (fmt, lint, build, test, e2e) before releasing
• Zips dist/ and attaches to GitHub Release with auto-generated notes
• Publishes MCP server to npm via NPM_TOKEN secret

Closes #209

Setup required

• Add NPM_TOKEN to repository secrets (Settings → Secrets → Actions)
  • Create a Granular Access Token on npmjs.com scoped to css-noop-checker-mcp

Release procedure

# 1. Bump version in package.json and mcp-server/package.json
# 2. Commit
git commit -am "chore: bump version to 0.2.0"
# 3. Tag and push
git tag v0.2.0
git push && git push --tags
# 4. Workflow runs automatically

Test plan

• Merge PR and add NPM_TOKEN secret
• Tag v0.1.0 on main to test the workflow
• Verify GitHub Release is created with zip artifact
• Verify npm package is published