- Database picker: switch/open/create databases from the UI with a file
  browser, recent list, and shared-file support (network drives, OneDrive)
- Lock files show who has a shared database open; stale locks auto-clean
- New databases created via the picker start empty (no demo data)
- Cross-platform config dir (Windows/macOS/Linux)
- Optional self-hosted log reporting via DCT_OS_LOG_URL (inert by default)
- docs/API.md: full REST endpoint reference
- README: shared database guide, macOS/Linux install, accurate feature list
- CHANGELOG: backfilled 0.2.0, added 0.3.0

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>