CB-544: shutdown drain preserves worker worktrees (no data loss)

bridged/src/test/java/dev/ltms/bridged/session/WorktreeSessionManagerTest.java

@@ -11,6 +11,7 @@ import org.junit.jupiter.api.Test;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.TimeUnit;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -125,6 +126,42 @@ class WorktreeSessionManagerTest {
         assertTrue(sessions.get(paneId).isEmpty(), "released session is no longer retrievable");
     }
 
+    @Test
+    void drainAllPreservesWorktreeOfIdleSession() {
+        FakeHerdr herdr = new FakeHerdr();
+        FakeWorktrees worktrees = new FakeWorktrees().withRepoRoot("/repo").withPrefix("/wt");
+        SessionManager sessions = new SessionManager(workerService(herdr), worktrees);
+        WorkerSession s = sessions.acquire("ltms-local", null, "/caller/proj", null,
+                new WorktreeRequest("cb-544", null));
+        sessions.asPresence().markPresent(s.terminalId()); // READY (idle)
+
+        sessions.drainAll(TimeUnit.MILLISECONDS.toNanos(100));
+
+        assertTrue(herdr.called("pane.close"), "shutdown drain still stops the worker pane");
+        assertTrue(worktrees.removeCalls().isEmpty(),
+                "shutdown drain must NOT remove the worktree — it is the only copy of the work");
+        assertTrue(sessions.roster().isEmpty(), "shutdown drain still deregisters the session");
+    }
+
+    @Test
+    void drainAllPreservesWorktreeOfSessionStillBusyAtTimeout() {
+        FakeHerdr herdr = new FakeHerdr();
+        FakeWorktrees worktrees = new FakeWorktrees().withRepoRoot("/repo").withPrefix("/wt");
+        SessionManager sessions = new SessionManager(workerService(herdr), worktrees);
+        WorkerSession s = sessions.acquire("ltms-local", null, "/caller/proj", null,
+                new WorktreeRequest("cb-544", null));
+        String terminal = s.terminalId();
+        sessions.asPresence().markPresent(terminal);
+        sessions.onDelivered(terminal); // BUSY, never completes → still BUSY when the timeout hits
+
+        sessions.drainAll(TimeUnit.MILLISECONDS.toNanos(100));
+
+        assertTrue(herdr.called("pane.close"), "shutdown drain stops the worker pane");
+        assertTrue(worktrees.removeCalls().isEmpty(),
+                "a session still BUSY at timeout must preserve its worktree unconditionally");
+        assertTrue(sessions.roster().isEmpty(), "shutdown drain still deregisters the session");
+    }
+
     @Test
     void sharedTreeReleaseMakesNoWorktreesCalls() {
         FakeHerdr herdr = new FakeHerdr();