[fix] Enable mouse gestures over video previews (#5279)

* [fix] Enable mouse gestures over video previews - fixes ctrl+scroll zoom and space+drag panning

🤖 Generated with [Claude Code](https://claude.ai/code)

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

* [improve] Enhance code clarity in media gesture handling with descriptive constants

* [clean] Remove dangling comment in handlePointer method

* [improve] Use satisfies and partial mocking for better type safety in tests

- Replace 'as any' with vi.mocked({partial: true}) for store mocks
- Use 'satisfies Partial<Event>' for better event type checking
- Remove 'not.toThrow' test as it tests default behavior
- Improve test readability and type safety per review feedback

* [improve] Test actual canvas existence check instead of side effects

- Replace vague 'graceful handling' test with specific 'early return' test
- Verify that getCanvas() is actually called to check canvas existence
- Test early return behavior when canvas is null rather than just preventDefault side effect
- More robust test that validates the intended logic flow

* [refactor] Use localized mocking instead of global mock functions

- Replace global mockGetCanvas and mockGet with in-situ vi.mocked() calls
- Extract store functions directly in test cases for better locality
- Follow DrJKL's suggestion for cleaner test structure
- Maintains same test coverage with improved readability

---------

Co-authored-by: Claude <noreply@anthropic.com>

src/composables/graph/useCanvasInteractions.ts

@@ -1,6 +1,7 @@
 import { computed } from 'vue'
 
 import { app } from '@/scripts/app'
+import { useCanvasStore } from '@/stores/graphStore'
 import { useSettingStore } from '@/stores/settingStore'
 
 /**
@@ -10,6 +11,7 @@ import { useSettingStore } from '@/stores/settingStore'
  */
 export function useCanvasInteractions() {
   const settingStore = useSettingStore()
+  const { getCanvas } = useCanvasStore()
 
   const isStandardNavMode = computed(
     () => settingStore.get('Comfy.Canvas.NavigationMode') === 'standard'
@@ -37,6 +39,27 @@ export function useCanvasInteractions() {
     // Otherwise, let the component handle it normally
   }
 
+  /**
+   * Handles pointer events from media elements that should potentially
+   * be forwarded to canvas (e.g., space+drag for panning)
+   */
+  const handlePointer = (event: PointerEvent) => {
+    // Check if canvas exists using established pattern
+    const canvas = getCanvas()
+    if (!canvas) return
+
+    // Check conditions for forwarding events to canvas
+    const isSpacePanningDrag = canvas.read_only && event.buttons === 1 // Space key pressed + left mouse drag
+    const isMiddleMousePanning = event.buttons === 4 // Middle mouse button for panning
+
+    if (isSpacePanningDrag || isMiddleMousePanning) {
+      event.preventDefault()
+      event.stopPropagation()
+      forwardEventToCanvas(event)
+      return
+    }
+  }
+
   /**
    * Forwards an event to the LiteGraph canvas
    */
@@ -54,6 +77,7 @@ export function useCanvasInteractions() {
 
   return {
     handleWheel,
+    handlePointer,
     forwardEventToCanvas
   }
 }