- 'mod+s' / 'mod+shift+s' / 'Tab' / etc.
- mod = meta (Mac) or ctrl (others)
- suppresses when <input>/<textarea>/contentEditable focused
- preventDefault on match
- TDD: 15 unit tests covering parser, match, suppression, unmount
- useCommandStore: register/unregister/registerMany/dispatch/get
- keyed by id (e.g. 'file.open', 'view.toggleSidebar')
- TDD: 10 unit tests covering register, dispatch, unregister, batch
- foundation for Phase 6 native menu + toolbar wiring