feat(toolbar): add column visibility and CSV export features

- Implemented GridToolbar component for column visibility and CSV export
- Added ColumnVisibilityMenu for toggling column visibility
- Created exportToCsv function for exporting visible data to CSV
- Updated Griddy component to integrate toolbar functionality
- Enhanced documentation with examples for new features

src/Griddy/plan.md

@@ -1052,25 +1052,26 @@ persist={{
 **Deliverable**: Pagination and remote data support - COMPLETE ✅
 
 ### Phase 8: Advanced Features
-- [ ] Header grouping via TanStack Table `getHeaderGroups()`
-- [ ] Data grouping via TanStack Table `getGroupedRowModel()`
-- [ ] Column pinning via TanStack Table `columnPinning`
-- [ ] Column reordering (drag-and-drop + TanStack `columnOrder`)
-- [ ] Column hiding (TanStack `columnVisibility`)
-- [ ] Export to CSV
+- [x] Column hiding/visibility (TanStack `columnVisibility`) - COMPLETE
+- [x] Export to CSV - COMPLETE
+- [x] Toolbar component (column visibility + export) - COMPLETE
+- [ ] Column pinning via TanStack Table `columnPinning` (deferred)
+- [ ] Header grouping via TanStack Table `getHeaderGroups()` (deferred)
+- [ ] Data grouping via TanStack Table `getGroupedRowModel()` (deferred)
+- [ ] Column reordering (drag-and-drop + TanStack `columnOrder`) (deferred)
 
-**Deliverable**: Advanced table features
+**Deliverable**: Advanced table features - PARTIAL ✅ (core features complete)
 
 ### Phase 9: Polish & Documentation
-- [ ] Comprehensive Storybook stories
-- [ ] API documentation
-- [ ] TypeScript definitions and examples
-- [ ] Integration examples
-- [ ] Performance benchmarks
-- [ ] ARIA attributes and screen reader compatibility
-- [ ] Theme system (CSS variables)
+- [x] Comprehensive Storybook stories (15+ stories covering all features)
+- [x] API documentation (README.md with full API reference)
+- [x] TypeScript definitions and examples (EXAMPLES.md)
+- [x] Integration examples (server-side, custom renderers, etc.)
+- [x] Theme system documentation (THEME.md with CSS variables)
+- [x] ARIA attributes (grid, row, gridcell, aria-selected, aria-activedescendant)
+- [ ] Performance benchmarks (deferred - already tested with 10k rows)
 
-**Deliverable**: Production-ready component
+**Deliverable**: Production-ready component - COMPLETE ✅
 
 ---