Fix macOS player window staying visible when starting PiP after a stop

MPVBackend.stop() clears the PiP bridge callbacks on macOS to prevent
crashes during window close, but the backend is reused across videos
and setupPiPIfNeeded is guarded by isPiPSetUp, so the callbacks were
never wired again. The next PiP session then started without notifying
PlayerService (no onPiPStatusChanged), leaving the player window
visible alongside the PiP window, both playing.

Extract the callback wiring into wirePiPBridgeCallbacks() and re-run it
in startPiP() and in setupPiPIfNeeded when already set up.

Yattee/Services/Player/MPVBackend.swift

@@ -1243,9 +1243,14 @@ final class MPVBackend: PlayerBackend {
 
         // Only proceed with actual setup if not already done and view is in window
         guard !isPiPSetUp, containerView.window != nil else {
-            // If already set up but playerState changed, update isPiPPossible
-            if isPiPSetUp, let playerState {
-                playerState.isPiPPossible = isPiPPossible
+            if isPiPSetUp {
+                // Re-wire bridge callbacks in case stop() cleared them since
+                // setup (the backend is reused across videos)
+                wirePiPBridgeCallbacks()
+                // If playerState changed, update isPiPPossible
+                if let playerState {
+                    playerState.isPiPPossible = isPiPPossible
+                }
             }
             return
         }
@@ -1278,6 +1283,20 @@ final class MPVBackend: PlayerBackend {
         // Set up the bridge with this backend and the container
         pipBridge.setup(backend: self, in: containerView)
 
+        wirePiPBridgeCallbacks()
+
+        // Manually notify current state now that callbacks are set up
+        pipBridge.notifyPiPPossibleState()
+    }
+
+    /// (Re)connect the PiP bridge callbacks. stop() clears them to prevent
+    /// crashes during window close, but the backend is reused across videos,
+    /// so they must be wired again before the next PiP session — otherwise
+    /// PiP starts without notifying PlayerService and the player window
+    /// stays visible alongside the PiP window.
+    private func wirePiPBridgeCallbacks() {
+        guard let pipBridge else { return }
+
         // Use the restore callback set by PlayerService
         pipBridge.onRestoreUserInterface = { [weak self] in
             await self?.onRestoreFromPiP?()
@@ -1331,9 +1350,6 @@ final class MPVBackend: PlayerBackend {
         pipBridge.onPiPRenderSizeChanged = { [weak self] size in
             self?._playerView?.updatePiPTargetSize(size)
         }
-
-        // Manually notify current state now that callbacks are set up
-        pipBridge.notifyPiPPossibleState()
     }
 
     /// Start Picture-in-Picture.
@@ -1343,6 +1359,10 @@ final class MPVBackend: PlayerBackend {
             return
         }
 
+        // Re-wire bridge callbacks in case stop() cleared them since setup
+        // (the backend is reused across videos)
+        wirePiPBridgeCallbacks()
+
         // Enable frame capture for PiP - start capturing BEFORE requesting PiP
         _playerView?.captureFramesForPiP = true