fix cross-process scenario switching and stale flights on scenario change

mcp_servers/data/scenarios/manager.py

@@ -15,7 +15,8 @@ class ScenarioManager:
     """Manages the active scenario. Singleton — all MCP servers share one instance."""
 
     def __init__(self) -> None:
-        self._active_id: str = "weather_disruption_ord"
+        import os
+        self._active_id: str = os.getenv("ACTIVE_SCENARIO") or os.getenv("DEFAULT_SCENARIO") or "weather_disruption_ord"
         self._cache: dict[str, Any] = {}
 
     @property