fix(copilot-acp): disable streaming path for CopilotACPClient

CopilotACPClient communicates via subprocess stdio and returns a plain
SimpleNamespace from _create_chat_completion(). The streaming path tries
to iterate this as a stream, crashing with:
  TypeError: 'types.SimpleNamespace' object is not iterable

Mirror the existing ACP exclusion pattern (used for Responses API upgrade)
to disable streaming when provider is copilot-acp or base_url starts with
acp:// or acp+tcp://.

Based on PR #9428 by @ningfangbin and issue #16271 by @Joseph19820124.

Fixes #16271

run_agent.py

@@ -10593,6 +10593,16 @@ class AIAgent:
                     # session instead of re-failing every retry.
                     if getattr(self, "_disable_streaming", False):
                         _use_streaming = False
+                    # CopilotACPClient communicates via subprocess stdio and
+                    # returns a plain SimpleNamespace — not an iterable
+                    # stream.  Mirror the ACP exclusion used for Responses
+                    # API upgrade (lines ~1083-1085).
+                    elif (
+                        self.provider == "copilot-acp"
+                        or str(self.base_url or "").lower().startswith("acp://copilot")
+                        or str(self.base_url or "").lower().startswith("acp+tcp://")
+                    ):
+                        _use_streaming = False
                     elif not self._has_stream_consumers():
                         # No display/TTS consumer. Still prefer streaming for
                         # health checking, but skip for Mock clients in tests