feat: add live demo dashboard on GitHub Pages

Add a demo mode to the dashboard that fetches graph data from Supabase
Storage instead of the local Vite dev server, bypasses the token gate,
and deploys alongside the homepage at /Understand-Anything/demo/.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/workflows/deploy-homepage.yml

@@ -5,6 +5,8 @@ on:
     branches: [main]
     paths:
       - 'homepage/**'
+      - 'understand-anything-plugin/packages/dashboard/**'
+      - 'understand-anything-plugin/packages/core/**'
       - '.github/workflows/deploy-homepage.yml'
   workflow_dispatch:
 
@@ -34,10 +36,23 @@ jobs:
       - name: Install dependencies
         run: pnpm install
 
-      - name: Build
+      - name: Build homepage
         working-directory: homepage
         run: pnpm build
 
+      - name: Build core
+        run: pnpm --filter @understand-anything/core build
+
+      - name: Build demo dashboard
+        run: pnpm --filter @understand-anything/dashboard build:demo
+        env:
+          VITE_GRAPH_URL: ${{ vars.DEMO_GRAPH_URL }}
+          VITE_DOMAIN_GRAPH_URL: ${{ vars.DEMO_DOMAIN_GRAPH_URL }}
+          VITE_META_URL: ${{ vars.DEMO_META_URL }}
+
+      - name: Merge demo into homepage output
+        run: cp -r understand-anything-plugin/packages/dashboard/dist homepage/dist/demo
+
       - uses: actions/upload-pages-artifact@v3
         with:
           path: homepage/dist