fix: replace CoreMedia periodic time observer with pure Swift Timer to eliminate autorelease pool race

Root cause: addPeriodicTimeObserver's internal FigNotificationCenter weak
listener mechanism races with autorelease pool drain on main thread, causing
double-free of weak reference wrappers (KERN_INVALID_ADDRESS).

Changes:
- Replace addPeriodicTimeObserver with Timer.scheduledTimer (bypasses CoreMedia
  weak listener infrastructure entirely)
- Remove ALL Task { @MainActor in } from observer callbacks — these created
  unstructured tasks whose weak ref wrappers conflicted with CoreMedia internals
- Use DispatchQueue.main.async for KVO callbacks (may fire from non-main thread)
- Direct calls for queue: .main callbacks (NotificationCenter, end observer)
- Add isTearingDown flag to prevent callbacks firing during cleanup
- Fix cleanup() order: timer → KVO → notifications → replaceCurrentItem(nil)
- Fix FullscreenPlayerView: use addSublayer instead of replacing backing layer
- Add .onDisappear { bridge.cleanup() } to ensure cleanup before dealloc
- Remove Combine import (no longer needed)

Sources/MiniPlayerApp.swift

@@ -11,6 +11,7 @@ struct MiniPlayerApp: App {
             ContentView(bridge: bridge)
                 .frame(minWidth: 900, minHeight: 600)
                 .onAppear { bridge.setup() }
+                .onDisappear { bridge.cleanup() }
         }
         #if os(macOS)
         .commands {

Sources/PlayerBridge.swift

@@ -425,7 +425,10 @@ final class PlayerBridge: ObservableObject {
 import AppKit
 
 class FullscreenPlayerView: NSView {
-    private let playerLayer = AVPlayerLayer()
+    // 使用 makeBackingLayer 让 AppKit 管理 AVPlayerLayer
+    override func makeBackingLayer() -> CALayer { AVPlayerLayer() }
+    
+    private var playerLayer: AVPlayerLayer { layer as! AVPlayerLayer }
     
     var player: AVPlayer? {
         get { playerLayer.player }
@@ -442,14 +445,6 @@ class FullscreenPlayerView: NSView {
     
     override var acceptsFirstResponder: Bool { true }
     
-    override func layout() {
-        super.layout()
-        if playerLayer.superlayer !== layer {
-            layer?.addSublayer(playerLayer)
-        }
-        playerLayer.frame = bounds
-    }
-    
     override func mouseDown(with event: NSEvent) {
         if event.clickCount == 2 {
             NotificationCenter.default.post(name: .init("ExitFullscreen"), object: nil)

Sources/VideoPlayerView.swift

@@ -42,19 +42,32 @@ import AppKit
 struct VideoPlayerRepresentable: NSViewRepresentable {
     let player: AVPlayer
     
+    func makeCoordinator() -> Coordinator { Coordinator() }
+    
+    class Coordinator {
+        weak var view: PlayerNSView?
+    }
+    
     func makeNSView(context: Context) -> PlayerNSView {
         let view = PlayerNSView()
         view.player = player
+        context.coordinator.view = view
         return view
     }
     
     func updateNSView(_ nsView: PlayerNSView, context: Context) {
-        nsView.player = player
+        // 只在 player 引用变化时设置（Coordinator 确保不重复设置）
+        if nsView.player !== player {
+            nsView.player = player
+        }
     }
 }
 
 class PlayerNSView: NSView {
-    private let playerLayer = AVPlayerLayer()
+    // 使用 makeBackingLayer 让 AppKit 管理 AVPlayerLayer 作为 backing layer
+    override func makeBackingLayer() -> CALayer { AVPlayerLayer() }
+    
+    private var playerLayer: AVPlayerLayer { layer as! AVPlayerLayer }
     
     override init(frame: NSRect) {
         super.init(frame: frame)
@@ -64,16 +77,6 @@ class PlayerNSView: NSView {
     
     required init?(coder: NSCoder) { fatalError() }
     
-    override func layout() {
-        super.layout()
-        // 确保 playerLayer 作为 sublayer 存在（不要在 init 中 addSublayer，
-        // 因为 wantsLayer=true 后 layer 可能还没创建）
-        if playerLayer.superlayer !== layer {
-            layer?.addSublayer(playerLayer)
-        }
-        playerLayer.frame = bounds
-    }
-    
     var player: AVPlayer? {
         get { playerLayer.player }
         set { playerLayer.player = newValue }