Adds design specification for user-defined Views — curated session
collections that span devices and replace the filtered gridViewMode.
Covers:
- Stable device identity prerequisite (device_id UUID in identity.json)
- Data model: views array in settings, active_view in state
- Three view tiers: All (virtual), user-created, Hidden (virtual)
- Mutual exclusion invariant between hidden and view membership
- UI: header dropdown view switcher, tile flyout menu, add sessions panel
- Migration strategy for session key format change
- Known limitations: rename breakage, atomic sync, shortcut cap
Brian Krabach