test(benchmarks): add A/B task fixtures with hidden checks

Ten small Python tasks, each failing on the fixture and passing with a
reference solution, including workflow expectations for a small change, a
bugfix, and a delegable change.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/benchmarks/tasks/01-small-config-change/repo/app/client.py

@@ -0,0 +1,6 @@
+from app.config import DEFAULT_TIMEOUT
+
+
+def request(url, timeout=None):
+    """Return the effective timeout in seconds; defaults to DEFAULT_TIMEOUT (30 seconds)."""
+    return timeout if timeout is not None else DEFAULT_TIMEOUT