Stabilize swipe gesture modifiers so 3D window survives UI auto-hide

The swipe modifiers branched on `enabled` with an if/else inside their
ViewModifier body. SwiftUI compiles that into a _ConditionalContent whose
branch flip reroots the wrapped view. Once `isSwipeEnabled` started
depending on `isUIHidden`, the auto-hide tick toggled the branch — and on
the RealityKit 3D path that tore down the ImagePresentationComponent, so
the immersive 3D window disappeared the moment the ornament hid.

Keep view identity constant by always attaching the gesture and gating
the work inside its onEnded closure instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: illixion

SpatialStash/SpatialStash/Views/Pictures/PhotoDisplayView.swift

@@ -718,17 +718,19 @@ private struct SwipeGestureModifier: ViewModifier {
     let enabled: Bool
     let onEnded: (CGFloat, CGFloat) -> Void
 
+    // Keep view identity stable across `enabled` flips: an if/else here
+    // produces a _ConditionalContent whose branch swap reroots the wrapped
+    // view. On the RealityKit 3D path that tears down the
+    // ImagePresentationComponent and the immersive window vanishes when the
+    // ornament auto-hides.
     func body(content: Content) -> some View {
-        if enabled {
-            content.gesture(
-                DragGesture(minimumDistance: 20)
-                    .onEnded { value in
-                        onEnded(value.translation.width, value.predictedEndTranslation.width)
-                    }
-            )
-        } else {
-            content
-        }
+        content.gesture(
+            DragGesture(minimumDistance: 20)
+                .onEnded { value in
+                    guard enabled else { return }
+                    onEnded(value.translation.width, value.predictedEndTranslation.width)
+                }
+        )
     }
 }
 
@@ -739,16 +741,13 @@ private struct EntitySwipeGestureModifier: ViewModifier {
     let onEnded: (CGFloat, CGFloat) -> Void
 
     func body(content: Content) -> some View {
-        if enabled {
-            content.gesture(
-                DragGesture(minimumDistance: 20)
-                    .targetedToAnyEntity()
-                    .onEnded { value in
-                        onEnded(value.translation.width, value.predictedEndTranslation.width)
-                    }
-            )
-        } else {
-            content
-        }
+        content.gesture(
+            DragGesture(minimumDistance: 20)
+                .targetedToAnyEntity()
+                .onEnded { value in
+                    guard enabled else { return }
+                    onEnded(value.translation.width, value.predictedEndTranslation.width)
+                }
+        )
     }
 }