fleetd #116: recover the already-gone-worktree teardown regression test

Ports the intent of the lost CB-576 commit c393600 (worker/cb576-01a04b-17,
never merged, package dev.ltms.bridged.*) onto main's dev.ltms.fleet.*
tree. Adds FakeWorktrees.markGone (tracks which add()'d worktree paths
still "exist", mirroring GitWorktrees.hasUncommitted's Files.exists guard
for the already-gone case) and a regression test,
releaseStillStopsPaneAndNotifiesWhenWorktreeIsGone, asserting that
SessionManager.release still fires notifyReleased, stops the pane, and
falls through to remove() when the worktree is already gone.

fleetd/src/test/java/dev/ltms/fleet/session/FakeWorktrees.java

@@ -45,6 +45,9 @@ public final class FakeWorktrees implements Worktrees {
     private final List<String> overlayShareOrder = new CopyOnWriteArrayList<>();
     private final Set<String> existingPaths = ConcurrentHashMap.newKeySet();
     private final Set<String> trackedPaths = ConcurrentHashMap.newKeySet();
+    /** Worktree paths that currently exist, mirroring GitWorktrees' {@code Files.exists} check for
+     *  the already-gone case (CB-576 review, fleetd #116). */
+    private final Set<String> worktreePaths = ConcurrentHashMap.newKeySet();
     private final AtomicLong snapshotSeq = new AtomicLong();
     private volatile RuntimeException addFailure;
     private volatile RuntimeException snapshotFailure;
@@ -115,7 +118,15 @@ public final class FakeWorktrees implements Worktrees {
         }
         // The branch already carries a unique nonce, so the derived path is distinct per acquire
         // without an extra counter — keep it a pure function of the branch the test can predict.
-        return prefix + "/" + branch.replace('/', '_');
+        String path = prefix + "/" + branch.replace('/', '_');
+        worktreePaths.add(path);
+        return path;
+    }
+
+    /** Model an operator / {@code git worktree prune} removing the worktree before release. */
+    public FakeWorktrees markGone(String worktreePath) {
+        worktreePaths.remove(worktreePath);
+        return this;
     }
 
     @Override
@@ -125,6 +136,11 @@ public final class FakeWorktrees implements Worktrees {
 
     @Override
     public boolean hasUncommitted(String worktreePath) {
+        // A path that was never added, or was marked gone, is reported clean, mirroring
+        // GitWorktrees' already-gone guard — never an error, so teardown still completes.
+        if (!worktreePaths.contains(worktreePath)) {
+            return false;
+        }
         return dirty;
     }
 

fleetd/src/test/java/dev/ltms/fleet/session/WorktreeSessionManagerTest.java

@@ -258,6 +258,38 @@ class WorktreeSessionManagerTest {
         }
     }
 
+    /**
+     * CB-576 review (fleetd #116). A worktree that is already gone (operator cleanup,
+     * {@code git worktree prune}, an earlier half-completed release) must not break teardown.
+     * {@code hasUncommitted} reports the missing path clean (mirroring {@code GitWorktrees}), so
+     * {@code release} still runs {@code notifyReleased} (the CB-516 fast-fail for a blocked
+     * {@code fleet_send} caller) and {@code launcher.stop} (so the pane is not orphaned), and falls
+     * through to the already-gone-tolerant {@code remove}. Since CB-581 this all happens because the
+     * notify-and-stop work sits in {@code release}'s {@code finally}/post-try block rather than a
+     * checked branch — this test pins that shape by construction.
+     */
+    @Test
+    void releaseStillStopsPaneAndNotifiesWhenWorktreeIsGone() {
+        FakeHerdr herdr = new FakeHerdr();
+        FakeWorktrees worktrees = new FakeWorktrees().withRepoRoot("/repo").withPrefix("/wt");
+        SessionManager sessions = new SessionManager(workerService(herdr), worktrees);
+        List<SessionManager.ReleaseDetail> released = new java.util.concurrent.CopyOnWriteArrayList<>();
+        sessions.onRelease(released::add);
+        MemberSession s = sessions.acquire("ltms-local", null, "/caller/proj", null,
+                new WorktreeRequest("cb-576g", null));
+
+        worktrees.markGone(s.worktree());
+        sessions.release(s.paneId());
+
+        assertEquals(1, released.size(),
+                "notifyReleased must still fire when the worktree is already gone (CB-516)");
+        assertEquals(s.terminalId(), released.getFirst().terminalId());
+        assertTrue(herdr.called("pane.close"),
+                "the pane must still be stopped when the worktree is already gone");
+        assertEquals(1, worktrees.removeCalls().size(),
+                "release still calls the already-gone-tolerant remove");
+    }
+
     @Test
     void drainAllPreservesWorktreeOfIdleSession() {
         FakeHerdr herdr = new FakeHerdr();