perf(agent-runner): improve session registry and orchestrator efficiency

- Add pre-computed _authorized_ids (frozenset) at session registration for O(1) lookup
- Refactor is_resource_allowed() from linear search to set membership check
- Add thread-safe locking to get_session_registry() singleton
- Cache _session_registry and _state_store references in orchestrator __init__
- Add asyncio.gather() for parallel resource building in AgentResourceBuilder
- Create shared test fixtures in tests/unit_tests/agent/conftest.py
- Update test files to import from shared conftest.py

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

src/langbot/pkg/agent/runner/result_normalizer.py

@@ -108,9 +108,13 @@ class AgentResultNormalizer:
             return None
 
         elif result_type == 'state.updated':
-            # Log for telemetry, don't yield
+            # Log for telemetry, don't yield to pipeline
+            # Orchestrator already handles the actual state_store.apply_update
+            scope = data.get('scope', 'conversation')  # Default for backward compat
+            key = data.get('key', 'unknown')
+            value_repr = repr(data.get('value', '...'))[:100]  # Truncate for log
             self.ap.logger.debug(
-                f'Runner {descriptor.id} state updated: {data.get("key", "unknown")}={data.get("value", "...")}'
+                f'Runner {descriptor.id} state.updated logged: scope={scope}, key={key}, value={value_repr}'
             )
             return None