#369 MEDIUM: Circuit breaker cache uses file system flag for reset

## Issue Circuit breaker cache reset in engine/tools/shell_command.py:63-84 relies on flag file /tmp/.highway_reset_circuit_breaker_cache: ## Impact - Race condition: multiple workers may clear cache simultaneously - Security: any process can trigger cache reset - Not portable to containers with isolated /tmp - Distributed systems: only resets on single node ## Location engine/tools/shell_command.py:63-84 ## Fix Use database-backed circuit breaker state for distributed coordination