Webapp: drop show_copy_button (absent in pinned gradio 6.14; crashed the Space at startup)

webapp/app.py

@@ -956,9 +956,11 @@ with gr.Blocks(title="CanLex", analytics_enabled=False) as demo:
     # carries the session's prior Q&A pairs so follow-ups have context.
     history_state = gr.State([])
     progress_md = gr.Markdown(value="")
-    answer_md = gr.Markdown(value=ANSWER_PLACEHOLDER, show_copy_button=True)
+    # (Gradio 6 dropped show_copy_button on Markdown -- shipping it crashed
+    # the Space at startup. The export button is the copy affordance.)
+    answer_md = gr.Markdown(value=ANSWER_PLACEHOLDER)
     with gr.Accordion("Retrieved source passages (every tool call)", open=False):
-        sources_md = gr.Markdown(show_copy_button=True)
+        sources_md = gr.Markdown()
     export_btn = gr.Button("Export research memo (.md)", size="sm")
     export_file = gr.File(label="Research memo", visible=False)