Release the background resources a discarded runtime owns

Several resources outlived a disconnect on purpose, which was harmless while a
process ran exactly one session for its whole life. They are now released when
the controller itself is closed:

- the ON4KST connection supervisor thread, which stopByUser did not touch
- the sked reminder scheduler, which had no shutdown at all
- the reachability executor, whose shutdown method existed but was never called
- the PSTRotator retry scheduler and its pending retry
- the map tile proxy, whose stop method existed but was never called, leaving a
  server socket and a twelve thread pool behind
- the station map bridge listeners and its coalescing animation, which would
  otherwise keep firing into a dead user interface

These are real leaks today; they only become visible when a second runtime is
built in the same process.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Hpa6bjie5qkeNG62y6FmXm

src/main/java/kst4contest/controller/ChatController.java

@@ -1083,9 +1083,35 @@ public class ChatController implements ThreadStatusCallback, PstRotatorEventList
 				rotatorClient.stop();
 				rotatorClient = null;
 			}
+
+			releaseBackgroundExecutors();
 		}
 	}
 
+	/**
+	 * Stops the background executors that live as long as this controller.
+	 *
+	 * <p>These are not bound to one ON4KST session, so disconnecting leaves them running
+	 * on purpose. When the controller itself is discarded they have to go, otherwise a
+	 * discarded controller stays reachable through its own threads.</p>
+	 */
+	private void releaseBackgroundExecutors() {
+
+		on4KstConnectionManager.shutdown();
+		skedReminderService.shutdown();
+
+		if (reachabilityService != null) {
+			reachabilityService.shutdown();
+		}
+
+		if (pendingRotatorRetry != null) {
+			pendingRotatorRetry.cancel(false);
+			pendingRotatorRetry = null;
+		}
+
+		rotatorCommandScheduler.shutdownNow();
+	}
+
 	private void cancelTimer(Timer timer) {
 		if (timer != null) {
 			timer.cancel();