[HexCodeYT]

Summary

Adds unsigned macOS release packaging for the PlainLink menu bar app and validates it in CI. This gives testers a zip artifact plus checksum while keeping signing and notarization out of scope for the MVP.

Details

• add scripts/package-macos-app.sh to build, smoke-test, zip, and checksum PlainLink.app
• name local packages as PlainLink-<version>-macos-<arch>.zip
• add a macOS GitHub Actions job that builds, tests, clippies, smoke-tests the app, packages it, and uploads the package artifacts
• extend the app bundle test to cover packaging script wiring
• document local packaging and checksum verification in README/macOS/menu bar docs
• update roadmap and contributor notes for unsigned release packages

Validation

• cargo fmt --check
• cargo test
• cargo clippy --all-targets -- -D warnings
• scripts/package-macos-app.sh
• shasum -a 256 -c PlainLink-0.1.0-macos-arm64.zip.sha256 from dist/packages

Notes

• The generated local package was dist/packages/PlainLink-0.1.0-macos-arm64.zip.
• Signing and notarization are still intentionally out of scope.