feat(demo): add Single/Loop play-mode buttons gated by isActivated

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

demo/Sources/WrapperTestView.swift

@@ -151,6 +151,22 @@ struct WrapperTestView: View {
                 Button("unbind") { runUnbind() }
                     .buttonStyle(.bordered)
             }
+
+            HStack {
+                Text("PlayMode")
+                    .font(.caption)
+                Spacer()
+                if let mode = viewModel.deviceInfo?.loop {
+                    Text(mode == .loop ? "循环" : "单播")
+                        .font(.caption)
+                        .foregroundColor(.secondary)
+                }
+                Button("Single") { runSetPlayMode(.single) }
+                    .buttonStyle(.bordered)
+                Button("Loop") { runSetPlayMode(.loop) }
+                    .buttonStyle(.bordered)
+            }
+            .disabled(!viewModel.isActivated || isBusy)
         }
     }
 
@@ -396,6 +412,22 @@ struct WrapperTestView: View {
         }
     }
 
+    private func runSetPlayMode(_ mode: PlayMode) {
+        isBusy = true
+        log("→ setPlayMode(\(mode == .loop ? "loop" : "single"), userId=\(userId))")
+        viewModel.sdk.setPlayMode(mode, userId: userId) { [self] result in
+            DispatchQueue.main.async {
+                self.isBusy = false
+                switch result {
+                case .success(let resp):
+                    self.log("setPlayMode ✓ sn=\(resp.sn)", level: .success)
+                case .failure(let error):
+                    self.log("setPlayMode ✗ \(error.localizedDescription)", level: .error)
+                }
+            }
+        }
+    }
+
     private func runTransfer() {
         isBusy = true
         log("→ transferMedia(\(fileUrl))")