fix(iOS): use UIKit UIActivityViewController directly instead of SwiftUI .sheet

SwiftUI multiple .sheet modifiers can conflict — replaced the pendingExportURL
sheet binding with a direct UIKit UIActivityViewController presentation from
the key window's root VC. This bypasses any SwiftUI sheet stack issues.

Also added copyLocalFile() for local file recording (FileManager.copyItem
instead of URLSession.download which fails on file:// URLs).

Sources/PlayerBridge.swift

@@ -178,10 +178,10 @@ final class PlayerBridge: ObservableObject {
         
         #if os(iOS)
         hlsRecorder.onRecordingSaved = { [weak self] url in
-            NSLog("[MiniPlayer] onRecordingSaved called, setting pendingExportURL: %@", url.lastPathComponent)
+            NSLog("[MiniPlayer] onRecordingSaved called: %@", url.lastPathComponent)
             self?.showToast("Saved: \(url.lastPathComponent)")
-            self?.pendingExportURL = url
-            NSLog("[MiniPlayer] pendingExportURL set to: %@", url.lastPathComponent)
+            // 直接用 UIKit present，不依赖 SwiftUI sheet binding
+            self?.presentShareSheet(for: url)
         }
         hlsRecorder.onError = { [weak self] msg in
             self?.showToast(msg)
@@ -190,6 +190,26 @@ final class PlayerBridge: ObservableObject {
     }
     
     #if os(iOS)
+    /// 直接通过 UIKit present UIActivityViewController，绕过 SwiftUI sheet 可能的多 sheet 冲突
+    func presentShareSheet(for url: URL) {
+        guard let windowScene = UIApplication.shared.connectedScenes
+            .compactMap({ $0 as? UIWindowScene })
+            .first(where: { $0.activationState == .foregroundActive })
+            ?? UIApplication.shared.connectedScenes.compactMap({ $0 as? UIWindowScene }).first
+        else { return }
+        
+        var topVC = windowScene.keyWindow?.rootViewController
+            ?? windowScene.windows.first(where: { !$0.isHidden && $0.bounds.size != .zero })?.rootViewController
+        while let presented = topVC?.presentedViewController { topVC = presented }
+        
+        let activityVC = UIActivityViewController(activityItems: [url], applicationActivities: nil)
+        activityVC.completionWithItemsHandler = { _, _, _, _ in
+            // 录制完成后可以删掉临时文件？不，用户可能需要再次分享
+        }
+        topVC?.present(activityVC, animated: true)
+        NSLog("[MiniPlayer] presentShareSheet: presented for %@", url.lastPathComponent)
+    }
+
     /// 配置 AVAudioSession，支持后台音频和 PiP
     private func ensureAudioSession() {
         let session = AVAudioSession.sharedInstance()