sync: Major UI updates from private repo (Jan 16-24)

Features synced:
- UI Panels Refactor: flexible pane system with ChatPane, NodePane,
  DimensionsPane, WorkflowsPane, ViewsPane, MapPane
- Source Content Reader: content type detection + 4 formatters
  (transcript, book, markdown, raw)
- Source Content Search: Cmd+F search in Source Reader
- Feed Layout Overhaul: LeftToolbar, SplitHandle, CollapsedRail
- Map Panel: promoted to first-class pane
- Edge policy simplification: auto-inference + direction correction

New files:
- src/components/panes/* (pane system)
- src/components/layout/CollapsedRail.tsx
- src/components/layout/LeftToolbar.tsx
- src/components/layout/SplitHandle.tsx
- src/components/focus/source/* (Source Reader + formatters)
- src/components/views/ViewsOverlay.tsx

Updated:
- ThreePanelLayout.tsx (complete refactor)
- FocusPanel.tsx (Source tab integration)
- API routes (dimensions GET, edges auto-inference)
- Database services (nodes, edges, dimensions)

Dependencies added:
- react-markdown
- remark-gfm

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/services/database/nodes.ts

@@ -78,10 +78,11 @@ export class NodeService {
 
     const result = sqlite.query<Node & { dimensions_json: string }>(query, params);
     
-    // Parse dimensions_json back to array for compatibility
+    // Parse dimensions_json and metadata back for compatibility
     return result.rows.map(row => ({
       ...row,
-      dimensions: JSON.parse(row.dimensions_json || '[]')
+      dimensions: JSON.parse(row.dimensions_json || '[]'),
+      metadata: row.metadata ? (typeof row.metadata === 'string' ? JSON.parse(row.metadata) : row.metadata) : null,
     }));
   }
 
@@ -109,7 +110,8 @@ export class NodeService {
     const row = result.rows[0];
     return {
       ...row,
-      dimensions: JSON.parse(row.dimensions_json || '[]')
+      dimensions: JSON.parse(row.dimensions_json || '[]'),
+      metadata: row.metadata ? (typeof row.metadata === 'string' ? JSON.parse(row.metadata) : row.metadata) : null,
     };
   }