useSettings Tests:
- Add test for null settings state protection
- Returns null immediately without calling APIs
- Prevents null pointer errors in save flow
- Add test for save mutation failure
- Verifies error propagates to caller
- Ensures restart flag remains untouched on failure
- Validates no side effects when save fails
useProviderActions Tests:
- Add error propagation tests for CRUD operations
- updateProvider: propagates errors to caller
- addProvider: propagates errors to caller
- deleteProvider: propagates errors to caller
- Add switch mutation error handling tests
- Claude switch: handles errors silently (no throw)
- Codex switch: skips plugin sync when mutation fails
- Verifies plugin sync APIs not called on failure
- Add loading state verification
- Test all mutations pending scenario (existing)
- Test all mutations idle scenario (new)
- Ensures isLoading flag accuracy
useImportExport Edge Case Tests (new file):
- Add test for user cancelling file dialog
- File dialog returns null (user cancelled)
- State remains unchanged (selectedFile: "", status: "idle")
- No error toast shown
- Add test for resetStatus behavior
- Clears error message and status
- Preserves selected file path for retry
- Resets backupId to null
All tests passing: 79/79 (10 new tests)