fix(stealth): suppress concealed disconnect messages

src/test/java/games/dmg/spigotstealth/StealthSessionListenerTest.java

@@ -10,9 +10,50 @@ import java.util.Map;
 import java.util.UUID;
 import org.bukkit.entity.Player;
 import org.bukkit.event.player.PlayerJoinEvent;
+import org.bukkit.event.player.PlayerQuitEvent;
 import org.junit.jupiter.api.Test;
 
 class StealthSessionListenerTest {
+    @Test
+    void concealedDisconnectSuppressesPublicAnnouncementBeforeCleanup() {
+        UUID playerId = UUID.randomUUID();
+        try (StealthStateManager manager = manager()) {
+            manager.update(state -> state.withPlayer(unlocked(playerId).withSession(false, true))).join();
+            QualifyingInvisibilityService progression = new QualifyingInvisibilityService(
+                    manager, Duration.ofHours(8), System::nanoTime, ignored -> { });
+            StealthSessionService sessions = new StealthSessionService(manager, progression);
+            StealthSessionListener listener = new StealthSessionListener(
+                    sessions, mock(IdentityPresentation.class), "Stealth active");
+            PlayerQuitEvent event = mock(PlayerQuitEvent.class);
+            Player player = player(playerId);
+            when(event.getPlayer()).thenReturn(player);
+
+            listener.onQuit(event);
+
+            verify(event).setQuitMessage(null);
+        }
+    }
+
+    @Test
+    void ordinaryDisconnectRetainsPublicAnnouncement() {
+        UUID playerId = UUID.randomUUID();
+        try (StealthStateManager manager = manager()) {
+            QualifyingInvisibilityService progression = new QualifyingInvisibilityService(
+                    manager, Duration.ofHours(8), System::nanoTime, ignored -> { });
+            StealthSessionListener listener = new StealthSessionListener(
+                    new StealthSessionService(manager, progression),
+                    mock(IdentityPresentation.class),
+                    "Stealth active");
+            PlayerQuitEvent event = mock(PlayerQuitEvent.class);
+            Player player = player(playerId);
+            when(event.getPlayer()).thenReturn(player);
+
+            listener.onQuit(event);
+
+            verify(event, never()).setQuitMessage(null);
+        }
+    }
+
     @Test
     void preparedLoginSuppressesAnnouncementAndConcealsIdentityForSession() {
         UUID playerId = UUID.randomUUID();