fix: reset touch state when iPad Safari loses focus (#7134)

## Summary
When the browser loses focus (e.g., switching apps, showing the dock),
touchend events may not fire, causing touchCount to remain non-zero.
This blocks all subsequent single-finger interactions since
processMouseDown returns early when touchCount > 0.

Added visibilitychange and touchcancel event listeners to reset touch
state when the page becomes hidden or touch is interrupted by the
system.

fix https://github.com/Comfy-Org/ComfyUI_frontend/issues/6721

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7134-fix-reset-touch-state-when-iPad-Safari-loses-focus-2be6d73d3650819abc7cf9c602909228)
by [Unito](https://www.unito.io)

src/extensions/core/simpleTouchSupport.ts

@@ -1,6 +1,6 @@
 import { LGraphCanvas, LiteGraph } from '@/lib/litegraph/src/litegraph'
 
-import { app } from '../../scripts/app'
+import { app } from '@/scripts/app'
 
 let touchZooming = false
 let touchCount = 0
@@ -82,6 +82,26 @@ app.registerExtension({
       }
     )
 
+    const resetTouchState = () => {
+      touchCount = 0
+      touchZooming = false
+      touchTime = null
+      lastTouch = null
+      lastScale = null
+      touchDist = null
+    }
+
+    // Reset touch state when page loses visibility (e.g., switching apps on iPad)
+    // This prevents touchCount from getting stuck when touchend events are missed
+    document.addEventListener('visibilitychange', () => {
+      if (document.hidden) {
+        resetTouchState()
+      }
+    })
+
+    // Also handle touchcancel which fires when touch is interrupted
+    app.canvasEl.parentElement?.addEventListener('touchcancel', resetTouchState)
+
     app.canvasEl.parentElement?.addEventListener(
       'touchmove',
       (e) => {