fix: cleanly stop CAT (and release relay handles) on shutdown — FlexRadio kept our API client registered, making the next launch take ~30s to reconnect

app.go

@@ -1193,8 +1193,15 @@ func (a *App) runShutdownTasks(ctx context.Context, steps []shutdownStep) {
 		a.emitShutdownEvent("shutdown:update", steps)
 	}
 	a.emitShutdownEvent("shutdown:done", steps)
-	// Give the UI a moment to show the "done" state before we yank the
+	// Cleanly tear down hardware links before quitting. Especially the CAT
-	// window away. 600ms feels purposeful without being annoying.
+	// backend: a FlexRadio keeps our API client registered until it notices the
+	// TCP is gone, and just letting the process exit left the slot stale — the
+	// NEXT launch then spent ~30s retrying the connect before the radio freed it.
+	// cat.Stop() closes the socket with a proper FIN so the radio drops us at once.
+	if a.cat != nil {
+		a.cat.Stop()
+	}
+	a.closeRelayDrivers() // release FTDI/serial relay handles for the next launch
 	time.Sleep(600 * time.Millisecond)
 	wruntime.Quit(ctx)
 }