Execution response regression evidence

Base: 67c738433a0c39ca93c97f8232a11879890d666b

Change: execution.public() removes slot_reserved from its result. The regression test covers rows both with and without that key.

Checks:

• PYTHONPATH=src python -m pytest -q -p no:cacheprovider — 528 passed, 279 skipped, exit 0.
• PYTHONPATH=src python scripts/test_postgres.py — 595 passed, 212 skipped, no test failures. All skips were due to listening sockets being unavailable in the agent sandbox. The wrapper returned exit 1 because it treats every skip as an acceptance failure, including these expected sandbox skips.