feat: expose showDebugPanel API and add panel toggle method

website/scripts/main.js

@@ -311,6 +311,9 @@ const debugPanel = new DebugPanel(debugPanelEl,
     }
 );
 
+// Browser DevTools command: showDebugPanel()
+window.showDebugPanel = () => debugPanel.show();
+
 // Connection SVG is screen-space — must re-render on every pan/zoom so paths track node positions.
 let hasTransformed = false;
 let trackTransform = false;