Explicit CPU default and GPU selector

app.py

@@ -9,6 +9,13 @@ def cpu_smoke():
 def gpu_smoke():
     return run_probe(True)
 
+def selected_smoke(backend):
+    if backend == 'cpu':
+        return cpu_smoke()
+    if backend == 'gpu':
+        return gpu_smoke()
+    raise ValueError('Choose CPU or GPU')
+
 with gr.Blocks() as demo:
     gr.Markdown('''# AI Learns To Drive — private compute test
 Simulator by [Zorro909](https://github.com/Zorro909/driving_sim_rs).
@@ -19,7 +26,9 @@ GPU uses up to 90 seconds of included allowance; check quota first. No automatic
 No user uploads; temporary model files are deleted before the receipt is returned.
 This tests backend execution, not useful learning, performance, or full UI integration.
 ''')
+    backend=gr.Radio(choices=[('CPU — no GPU allowance needed','cpu'),('GPU — uses included GPU allowance','gpu')],value='cpu',label='Compute')
     report=gr.JSON(label='Execution receipt')
+    gr.Button('Run selected backend',variant='primary').click(selected_smoke,inputs=backend,outputs=report,api_name='selected_smoke',concurrency_limit=1,concurrency_id='native')
     gr.Button('Run CPU-only test').click(cpu_smoke,outputs=report,api_name='cpu_smoke',concurrency_limit=1,concurrency_id='native')
     gr.Button('Run GPU test').click(gpu_smoke,outputs=report,api_name='gpu_smoke',concurrency_limit=1,concurrency_id='native')