完善 OTG 相机有线传图：支持 Sony/Canon 自动识别，页面 detach 保持会话以便再次进入复连。

引入进程级 CameraTetheringSession 与共享 USB Browser；离开传图页仅取消 UI 回调，App 终止时再完整 shutdown 释放 PTP 与 Browser 资源。

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkanTests/CameraTethering/CameraTetheringSessionTests.swift

@@ -0,0 +1,24 @@
+//
+//  CameraTetheringSessionTests.swift
+//  suixinkanTests
+//
+
+import XCTest
+@testable import suixinkan
+
+/// CameraTetheringSession 与 detach/shutdown 语义测试。
+@MainActor
+final class CameraTetheringSessionTests: XCTestCase {
+    func testSharedServiceIsAutoDetectInstance() {
+        XCTAssertTrue(CameraTetheringSession.sharedService is AutoDetectCameraService)
+    }
+
+    func testDetachFromUIClearsCallbacksWithoutChangingConnectionState() {
+        let service = AutoDetectCameraService()
+        service.onConnectionStateChange = { _ in }
+        service.onNewAsset = { _ in }
+        service.detachFromUI()
+        XCTAssertNil(service.onConnectionStateChange)
+        XCTAssertNil(service.onNewAsset)
+    }
+}