- Remove deprecated macos-13 runner
- Add macos-14 and macos-15 (M1 runners)
- Update Node matrix: drop EOL v16, add v22
- Upgrade actions/checkout v2 -> v4, actions/setup-node v1 -> v4
- Remove redundant chmod (handled by postbuild.js)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>