useBulkActions was embedded in App.tsx with zero test coverage. It handles
bulk archive, trash, and restore operations — all with partial-failure
semantics and toast messaging.
Extract to src/hooks/useBulkActions.ts and add 15 unit tests covering:
- Plural/singular toast messages ("2 notes archived" vs "1 note archived")
- Partial failures: only successful operations counted in toast
- All-failure case: no toast shown
- Empty array: no operations called, no toast
Risk mitigated: silent bugs in batch operations (wrong count in toast,
toast shown when nothing succeeded, partial failure not handled).
Co-authored-by: Test <test@test.com>
