Add one-click fixture UI

app.py

@@ -17,6 +17,7 @@ with gr.Blocks(title="Simam Neural Codec Lab") as demo:
         video = gr.Video(label="Short source clip")
         report = gr.Markdown("Upload a clip, then run the benchmark.")
     run = gr.Button("Run codec comparison", variant="primary")
+    gr.Examples([["examples/sample_codec.mp4"]], inputs=[video], label="Try the included synthetic fixture")
     outputs = gr.Files(label="Generated comparison files")
     run.click(analyze, inputs=video, outputs=[report, outputs])
     gr.Markdown("### Research boundary\nThis baseline uses host FFmpeg encoders. It is the control group for future learned-codec adapters; it does not claim neural compression superiority.")