Implemented thread-safety improvements for ContextTierService by
introducing a re-entrant lock and guarding all critical sections
with self._lock. This prevents RuntimeError: dictionary changed
size during iteration under concurrent plan execution.
- Added threading.RLock to ContextTierService.__init__ as self._lock
- Wrapped all public methods (store, get, promote, demote, evict_lru,
get_metrics, get_all_fragments, get_hot_fragments, get_for_actor,
get_scoped_view) with with self._lock:
- Added _lock: threading.RLock type stub to TierRuntimeMixin and
ScopedTierMixin
- Wrapped enforce_staleness in TierRuntimeMixin with self._lock
- Wrapped get_scoped_by_resource and get_scoped_metrics in
ScopedTierMixin with self._lock
- Extracted settings helpers to new context_tier_settings.py to keep
context_tiers.py under 500 lines
- Added BDD feature file context_tier_thread_safety.feature with
10 thread-safety scenarios
- Added step definitions context_tier_thread_safety_steps.py
- Updated CHANGELOG.md with fix entry
ISSUES CLOSED: #7547
