robustness: vision/depth render off the event loop (deepcopy snapshot), chat auto-reconnect + friendly errors, demo catches connection failures

testbed/demo.py

@@ -152,7 +152,9 @@ async def run_llm_agent(
         log=lambda role, msg: print(f"[{role}] {msg}"),
     )
     try:
-        return await run_llm_agent_loop(controller, max_steps, log=print_log, recorder=recorder)
+        return await run_llm_agent_loop(
+            controller, max_steps, log=print_log, recorder=recorder
+        )
     except RuntimeError as exc:
         return {"steps": 0, "tool_calls": 0, "result": str(exc), "interacted": False}
 
@@ -398,7 +400,14 @@ def main() -> int:
         "into this directory, plus demo.gif animation and demo_summary.png",
     )
     args = parser.parse_args()
-    summary = asyncio.run(run_demo(args))
+    try:
+        summary = asyncio.run(run_demo(args))
+    except KeyboardInterrupt:
+        return 2
+    except Exception as exc:  # noqa: BLE001 - friendly failure instead of a traceback
+        print(f"\n[demo] failed: {type(exc).__name__}: {exc}")
+        print("[demo] is the bridge running?  scripts/run_bridge.sh")
+        return 1
     return 0 if summary.get("interacted") else 1