sync: contextual substrate UX from private repo

- Add DimensionIconsContext for app-wide dimension icon sharing
- Enhanced getNodeIcon() with favicon/YouTube/PDF detection + dimension icons
- Propagate dynamic icons to GridView, ListView, SearchModal, FocusPanel, ViewsOverlay, FolderViewOverlay
- Add RahEdge component with hover labels for map edges
- Update RahNode with dimension-colored borders and icon support
- Add MiniMap with dimension color coding to MapPane
- MCP server: add description field to rah_update_node, bump standalone to v1.4.2

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

apps/mcp-server-standalone/index.js

@@ -78,6 +78,7 @@ const updateNodeInputSchema = {
   id: z.number().int().positive().describe('Node ID'),
   updates: z.object({
     title: z.string().optional().describe('New title'),
+    description: z.string().optional().describe('New description (overwrites existing)'),
     content: z.string().optional().describe('Content to APPEND'),
     link: z.string().optional().describe('New link'),
     dimensions: z.array(z.string()).optional().describe('New dimensions (replaces existing)'),