Add public release infrastructure with Sparkle auto-update support
- Configure Sparkle EdDSA key (SUPublicEDKey) and feed URL in Info.plist
- Switch version scheme from semver to date-based YYYY.M.DD format
- Add release.sh: full pipeline with archive, re-sign, DMG, notarize, appcast
- Add install-release Makefile target for local Release test builds
- Split /fork-release into /sync-upstream (sync only) and /release (publish)
- Deprecate release-to-fork.sh in favor of release.sh
- Update docs: fork-sync-and-release.md, change-list.md, CLAUDE.md, AGENTS.md