fix: enable touch panning and prevent page scroll on mobile

- Add touch-action: none on canvas to prevent browser scroll hijack
- Single-finger touch on empty canvas now triggers pan (pointerType check)
- Fix page bounce on mobile with position: fixed and 100dvh height

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

src/App.jsx

@@ -91,10 +91,17 @@ export default function App({ onSwitchToGame }) {
       state.panStart = { x: e.clientX - state.camX, y: e.clientY - state.camY };
       e.preventDefault();
     } else if (e.button === 0 && !connectingRef.current) {
+      // On mobile (touch), single finger on empty canvas = pan
+      if (isMobile && e.pointerType === 'touch') {
+        state.panning = true;
+        state.panStart = { x: e.clientX - state.camX, y: e.clientY - state.camY };
+        e.preventDefault();
+        return;
+      }
       state.selectedModuleId = null;
       emit();
     }
-  }, []);
+  }, [isMobile]);
 
   const handlePointerMove = useCallback((e) => {
     if (state.panning && state.panStart) {

src/game/PuzzleView.jsx

@@ -131,10 +131,17 @@ export default function PuzzleView({ level, levelIndex, worldLevels, onBack, onN
       state.panStart = { x: e.clientX - state.camX, y: e.clientY - state.camY };
       e.preventDefault();
     } else if (e.button === 0 && !connectingRef.current) {
+      // On mobile (touch), single finger on empty canvas = pan
+      if (isMobile && e.pointerType === 'touch') {
+        state.panning = true;
+        state.panStart = { x: e.clientX - state.camX, y: e.clientY - state.camY };
+        e.preventDefault();
+        return;
+      }
       state.selectedModuleId = null;
       emit();
     }
-  }, []);
+  }, [isMobile]);
 
   const handlePointerMove = useCallback((e) => {
     if (state.panning && state.panStart) {

src/index.css

@@ -802,6 +802,10 @@ html, body, #root {
 
 @media (max-width: 768px) {
 
+  /* --- Prevent page scroll/bounce --- */
+  html, body, #root { overflow: hidden; position: fixed; width: 100%; height: 100%; }
+  .app, .gm-puzzle { overflow: hidden; height: 100dvh; }
+
   /* --- Sandbox Toolbar --- */
   .toolbar { height: 44px; padding: 0 12px; gap: 6px; }
   .toolbar-title { font-size: 13px; letter-spacing: 0.8px; }
@@ -924,7 +928,7 @@ html, body, #root {
   }
 
   /* --- Canvas adjustments --- */
-  .node-canvas { cursor: default; }
+  .node-canvas { cursor: default; touch-action: none; }
   .zoom-controls { right: 8px; top: 8px; }
   .zoom-btn { width: 40px; height: 36px; min-height: 44px; }
   .port-dot { width: 18px; height: 18px; }