fix(copilot): address review comments — wait_for_stash fast path, error marker, compat test

- Add fast path in wait_for_stash: check event.is_set() before clearing
  to avoid unnecessary 0.5s timeout when PostToolUse hook completes
  before the streaming loop calls wait_for_stash
- Tighten "failed" error marker to "failed to" in _is_tool_error_or_denial
  to avoid matching benign outputs like "3 tests failed"
- Add max_buffer_size to SDK compat test fields_we_use

autogpt_platform/backend/backend/copilot/sdk/response_adapter_test.py

@@ -569,15 +569,10 @@ async def test_wait_for_stash_already_stashed():
 
     # Stash before waiting — simulates hook completing before message arrives
     _stash("Read", "file contents")
-    # Event is now set; wait_for_stash clears it and re-waits.
-    # Since the stash already happened, the event won't fire again,
-    # so this should timeout. But the stash DATA is available.
+    # Event is now set; wait_for_stash detects the fast path and returns
+    # immediately without timing out.
     result = await wait_for_stash(timeout=0.05)
-    # Returns False because the event was cleared before waiting and
-    # no NEW signal arrived. This is expected: the flush will find the
-    # data in the stash directly — wait_for_stash is only needed when
-    # the stash hasn't happened yet.
-    assert result is False
+    assert result is True
 
     # But the stash itself is populated
     assert _pto.get({}).get("Read") == ["file contents"]

autogpt_platform/backend/backend/copilot/sdk/sdk_compat_test.py

@@ -104,6 +104,7 @@ def test_agent_options_accepts_all_our_fields():
         "model",
         "env",
         "resume",
+        "max_buffer_size",
     ]
     sig = inspect.signature(ClaudeAgentOptions)
     for field in fields_we_use:

autogpt_platform/backend/backend/copilot/sdk/service.py

@@ -459,7 +459,7 @@ def _is_tool_error_or_denial(content: str | None) -> bool:
             "maximum",  # subtask-limit denial
             "denied",
             "blocked",
-            "failed",  # internal tool execution failures
+            "failed to",  # internal tool execution failures
             '"iserror": true',  # MCP protocol error flag
         )
     )

autogpt_platform/backend/backend/copilot/sdk/tool_adapter.py

@@ -169,11 +169,15 @@ async def wait_for_stash(timeout: float = 0.5) -> bool:
     event = _stash_event.get(None)
     if event is None:
         return False
-    # Clear before waiting so we detect new signals only.
-    event.clear()
+    # Fast path: hook already completed before we got here.
+    if event.is_set():
+        event.clear()
+        return True
+    # Slow path: wait for the hook to signal.
     try:
         async with asyncio.timeout(timeout):
             await event.wait()
+        event.clear()
         return True
     except TimeoutError:
         return False