feat(KB-048): add collapsible list sections to dashboard

- Add section expansion state management with localStorage persistence
- Update section headers with chevron toggle controls
- Implement conditional task row rendering based on section state
- Add Expand All / Collapse All toolbar controls
- Add CSS styles for chevron rotation animation and section headers
- Add comprehensive tests for collapsible section behavior

.gitignore

@@ -5,6 +5,9 @@ node_modules/
 dist/
 *.tsbuildinfo
 
+# Coverage reports
+coverage/
+
 # hai runtime (local board state — don't commit)
 .kb/
 .hai/