Merge #274 (PR #277): clean up the worktree when add() fails after creating it

GitWorktrees.add() created the worktree and branch, then ran more steps that
can throw — requireCredentialFreeHttpsOrigin among them, which is an
intended security refusal, not an IO accident. Any throw meant add() never
returned, so SessionManager.acquireWithWorktree never learned the path, its
'if (path != null)' cleanup could not fire, and the worktree and branch
leaked with nothing tracking them. Every OTHER exit from that method was
cleaned up correctly; only the exits inside add() were uncounted.

add() now cleans up what it created before rethrowing, reusing remove() and
additionally deleting the branch — a branch that never finished provisioning
has no session and no PR behind it. Worktree first, since a checked-out
branch cannot be deleted. Cleanup failure is logged and never masks the
original exception.

Verified by me: the real merge into current main builds green (1281 tests),
and I reran the mutation myself without git stash — dropping the cleanup
call fails the new test with 'the worktree directory leaked after a
post-creation step threw'.

The test drives add() itself through the existing afterWorktreeAdded seam,
so the failure happens after the worktree exists rather than downstream in
another caller.

fleetd/src/main/java/dev/ltms/fleet/session/GitWorktrees.java

@@ -167,14 +167,59 @@ public final class GitWorktrees implements Worktrees {
         log.info("adding worktree branch={} path={} base={}", branch, wt, base);
         removeUserInfoFromHttpsOrigin(repoRoot);
         exec("git", "-C", repoRoot, "worktree", "add", wt, "-b", branch, base);
-        afterWorktreeAdded.accept(wt);
-        requireCredentialFreeHttpsOrigin(wt);
-        configureEnvironmentCredentialHelper(repoRoot, wt);
-        configureHttpsUrlRewriteForSshOrigin(repoRoot, wt);
-        isolateToolSurface(wt);
+        try {
+            afterWorktreeAdded.accept(wt);
+            requireCredentialFreeHttpsOrigin(wt);
+            configureEnvironmentCredentialHelper(repoRoot, wt);
+            configureHttpsUrlRewriteForSshOrigin(repoRoot, wt);
+            isolateToolSurface(wt);
+        } catch (RuntimeException e) {
+            cleanupAfterAddFailure(repoRoot, wt, branch, e);
+            throw e;
+        }
         return wt;
     }
 
+    /**
+     * {@code add()} has already created the worktree and its branch by the time any step from
+     * {@link #afterWorktreeAdded} through {@link #isolateToolSurface} can throw — including
+     * {@link #requireCredentialFreeHttpsOrigin}, an intended security refusal, not only an IO
+     * accident. Without this, {@code add()} never returns, so its caller
+     * ({@code SessionManager#acquireWithWorktree}) never receives a path to register or clean up:
+     * its local {@code path} stays null, the {@code if (path != null)} guard in its own catch block
+     * never runs, and the worktree directory and branch leak on disk forever with nothing tracking
+     * them (fleetd #274).
+     *
+     * <p>Reuses {@link #remove} — the same {@code git worktree remove --force} path every other
+     * cleanup exit in this class already goes through — rather than a bespoke removal. It
+     * additionally deletes {@code branch}: {@link #remove} alone deliberately leaves a released
+     * session's branch behind (a worker's branch is expected to outlive its worktree, for PRs and
+     * recovery), but a branch that never finished provisioning has no session, no PR, and nothing
+     * else pointing at it, so leaving it behind would just trade one leak for a smaller one. Forced
+     * (`-D`) because the branch is new and unmerged by construction. The worktree is removed first:
+     * a branch checked out by a worktree cannot be deleted until the worktree that holds it is gone.
+     *
+     * <p>Cleanup failure must never mask {@code original} — that is the exception that explains
+     * what actually went wrong — so a failure here is only logged, matching the pattern already
+     * used in {@code SessionManager#acquireWithWorktree}'s own catch block.
+     */
+    private void cleanupAfterAddFailure(String repoRoot, String worktreePath, String branch, RuntimeException original) {
+        log.warn("provisioning failed for branch={} path={}: {} — cleaning up before rethrowing",
+                branch, worktreePath, original.getMessage());
+        try {
+            remove(repoRoot, worktreePath);
+        } catch (RuntimeException cleanup) {
+            log.warn("failed to remove leaked worktree {} after provisioning error: {}",
+                    worktreePath, cleanup.getMessage());
+        }
+        try {
+            exec("git", "-C", repoRoot, "branch", "-D", branch);
+        } catch (RuntimeException cleanup) {
+            log.warn("failed to remove leaked branch {} after provisioning error: {}",
+                    branch, cleanup.getMessage());
+        }
+    }
+
     /**
      * A linked worktree shares its primary checkout's git config. Remove HTTPS user info before
      * adding one, so a credential accidentally embedded in that config cannot reach the member.

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

@@ -21,6 +21,7 @@ import java.util.Map;
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.TimeUnit;
+import java.util.concurrent.atomic.AtomicReference;
 
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -362,6 +363,46 @@ class GitWorktreesTest {
         assertEquals("worktree origin contains HTTPS user info; refusing provision", error.getMessage());
     }
 
+    /**
+     * fleetd #274. {@code add()} creates the worktree and its branch, then runs several more steps
+     * that can throw — {@code requireCredentialFreeHttpsOrigin} among them, an intended security
+     * refusal, not an IO accident. Before the fix, any exception from those later steps left
+     * {@code add()} never returning, so its caller never learned the path and the worktree
+     * directory plus its branch leaked on disk forever with nothing tracking them.
+     *
+     * <p>This drives the exact same {@code afterWorktreeAdded} test seam as
+     * {@link #provisioningRefusesAWorktreeWhoseOriginStillHasHttpsUserInfo} — a mutation applied
+     * right after {@code git worktree add}, so the step that throws
+     * ({@code requireCredentialFreeHttpsOrigin}, reached moments later inside {@code add()} itself)
+     * runs strictly after the worktree and branch already exist, not downstream of {@code add()}
+     * in some other caller. {@code afterWorktreeAdded} also hands back the created path, so the
+     * assertions below don't have to guess the generated nonce.
+     */
+    @Test
+    void addCleansUpTheWorktreeAndBranchWhenAPostCreationStepThrows(@TempDir Path tmp) throws Exception {
+        Path repo = initRepo(tmp.resolve("repo"));
+        git(repo, "remote", "add", "origin", "https://git.ltms.dev/akb/kb.git");
+        String branch = "cb-274-leak";
+        AtomicReference<String> createdPath = new AtomicReference<>();
+        GitWorktrees worktrees = new GitWorktrees(tmp.resolve("wts").toString(), worktreePath -> {
+            createdPath.set(worktreePath);
+            try {
+                git(Path.of(worktreePath), "remote", "set-url", "origin",
+                        "https://synthetic-test-token@git.ltms.dev/akb/kb.git");
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
+        });
+
+        assertThrows(WorktreeException.class, () -> worktrees.add(repo.toString(), branch, "HEAD"));
+
+        assertNotNull(createdPath.get(), "afterWorktreeAdded must have run with the created path");
+        assertFalse(Files.exists(Path.of(createdPath.get())),
+                "the worktree directory leaked after a post-creation step threw");
+        String heads = forEachRef(repo, "refs/heads/" + branch);
+        assertTrue(heads.isBlank(), "the branch leaked after a post-creation step threw:\n" + heads);
+    }
+
     // ---- CB-189: broader remote-URL coverage — every remote, both fetch and push URLs, any
     // non-SSH scheme. Reporting only, additive to the origin/https strip-and-refuse tests above. ----