New molecules:
- Tree: recursive file/skill browser with expand/collapse (JS.toggle),
  icon slot, selected/disabled states — no hook required
- MarkdownEditor: 10-action toolbar, Edit/Preview/Split modes, live
  preview via phx-change + MDEx; requires MarkdownEditor hook
- Kanban: multi-column DnD board (native HTML5, no external deps),
  fires kanban_card_moved LiveView event; requires Kanban hook

New JS hooks: MarkdownEditor, Kanban
Storybook stories for all three components
Live demo blocks added to ThemeLive dashboard (blocks 21-23)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>