fix(tests): correct assert in test_sanitize_agent_error_stderr_and_exc

The exc class IS the tag when stderr is provided:
  "Agent error (ValueError): rate limit exceeded"

Fixes the incorrect assertion added in PR #517.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

workspace/tests/test_executor_helpers.py

@@ -761,7 +761,7 @@ def test_sanitize_agent_error_stderr_and_exc():
     """exception + stderr: exc type is the tag, stderr is the body."""
     err = ValueError("this should not appear")
     out = sanitize_agent_error(exc=err, stderr="rate limit exceeded")
-    assert "ValueError" not in out  # exc class is overridden by stderr
+    assert "ValueError" in out  # exc class IS the tag when stderr is provided
     assert "rate limit exceeded" in out