fix: Disable download button until content exists - prevent empty download field UX issue

- Download button now disabled by default (interactive=False)
- Button only enables after successful generation completes
- Uses .then() chain to enable button after streaming finishes
- Hidden download_output component for cleaner UX

app.py

@@ -1029,7 +1029,10 @@ def create_interface():
                     with gr.Row():
                         copy_summary_btn = gr.Button("📋 Copy Summary", size="sm")
                         copy_thinking_btn = gr.Button("📋 Copy Thinking", size="sm")
-                        download_btn = gr.Button("⬇️ Download (JSON)", size="sm")
+                        download_btn = gr.Button("⬇️ Download (JSON)", size="sm", interactive=False)
+                    
+                    # Hidden file output for download (not shown until ready)
+                    download_output = gr.File(label="Download", visible=False)
         
         # Event handlers
         submit_btn.click(
@@ -1037,6 +1040,9 @@ def create_interface():
             inputs=[file_input, model_dropdown, enable_reasoning, max_tokens, temperature_slider, top_p, top_k, language_selector],
             outputs=[thinking_output, summary_output, info_output, metrics_state],
             show_progress="full"
+        ).then(
+            fn=lambda: gr.Button(interactive=True),
+            outputs=[download_btn]
         )
         
         model_dropdown.change(
@@ -1064,7 +1070,7 @@ def create_interface():
         download_btn.click(
             fn=download_summary_json,
             inputs=[summary_output, thinking_output, model_dropdown, language_selector, metrics_state],
-            outputs=[gr.File(label="Download")]
+            outputs=[download_output]
         )
         
         # Footer