Add threading.RLock to InvariantService to protect shared state
(_invariants dict, _enforcement_records list) from concurrent access
by multiple threads during parallel plan execution. Prevents
RuntimeError: dictionary changed size during iteration and data
corruption in multi-threaded environments.
Changes:
- Added self._lock = RLock() in __init__
- Wrapped all public methods (add_invariant, list_invariants,
remove_invariant, get_effective_invariants, enforce_invariants)
with lock acquisition via context managers
- Added helper read methods: get_enforcement_records(), get_invariant(),
get_invariants_snapshot() -- all thread-safe
- Added BDD tests for concurrent access patterns
- Updated CHANGELOG.md and CONTRIBUTORS.md
ISSUES CLOSED: #7524
HAL9000
7470f98155