fix(minecraft): nullify EventRegistry context on stop() to prevent stale handler execution

When stop() is called before detachFromBot(), mineflayer listeners remain
attached. Nullifying context ensures handleMineflayerEvent's guard clause
silently ignores any events that fire in this window.

services/minecraft/src/cognitive/perception/events/index.ts

@@ -96,6 +96,10 @@ export class EventRegistry {
       clearInterval(this.timer)
       this.timer = null
     }
+    // NOTICE: Nullify context so that any stale mineflayer listeners that fire
+    // after stop() (but before detachFromBot()) are silently ignored by the
+    // guard at the top of handleMineflayerEvent.
+    this.context = null
   }
 
   public getDebugSnapshot(): SaliencySnapshot {