Show progress while the Start workflow intent runs

mac/Sources/Byre/QuickRun.swift

@@ -169,11 +169,20 @@ struct QuickRunPage: View {
                 .disabled(starting)
                 Spacer()
                 if let choice {
-                    Button("Start") {
+                    if starting {
+                        ProgressView()
+                    }
+                    Button {
                         start(choice, prompt)
+                    } label: {
+                        ZStack {
+                            Text("Starting…")
+                                .hidden()
+                            Text(starting ? "Starting…" : "Start")
+                        }
                     }
                     .buttonStyle(WebButtonStyle(primary: true))
-                    .disabled(prompt.isEmpty || starting)
+                    .disabled(prompt.isEmpty)
                 }
             }
             .font(Fonts.font(15, weight: 700))