fix(issue-6): fail-closed registry timeout and TUI turn handshake

- Introduce finalize_unfinished in multi-agent-mux-delegate-job for fail-closed atomic transitions
- Enforce CAS dispatch_token and attempt_id pinning across engine, CLI, and lifecycle scripts
- Integrate Herdr wait_for_agent_idle turn handshake to prevent prompt loss and race conditions
- Resolve bash 3.2 set -u empty array expansion compatibility in lib.sh
- Preserve Issue #5 R2 contract in CAS transition engine (engine.py, publish_event.py, service.py)
- Add comprehensive regression suites (test_issue6_fail_closed.py, test_issue6_turn_handshake.py)
- Bump lockstep framework and skills to v4.4.1 across lib.sh, eager.py, VERSIONS.md, 8 SKILL.md
- Synchronize documentation (IMPROVEMENTS.md, MESSAGING.md, state-transitions.md, task.md, phase5-e2e.md)
- Unanimous PASS achieved across 4 reviewer team leaders (Claude, Codex, OpenCode, Grok)

Closes #6

.agents/skills/lib_py/delegation/registry.py

@@ -100,6 +100,8 @@ def register_job(
         "reviewer_session": reviewer_session,
         "max_iterations": int(max_iterations),
         "iteration": 1,
+        "dispatch_token": uuid.uuid4().hex,
+        "attempt_id": 1,
     }
     with registry_lock(registry_dir):
         if mqtt_common._job_path(job_id, registry_dir).exists():
@@ -299,8 +301,15 @@ def _build_parser() -> argparse.ArgumentParser:
     p_update.add_argument("--agent-session", default=None)
     p_update.add_argument("--prompt", default=None)
     p_update.add_argument("--iteration", type=int, default=None)
+    p_update.add_argument("--attempt-id", type=int, default=None)
     p_update.add_argument("--role", default=None)
 
+    p_close = sub.add_parser("close", help="close a job with deadline_timeout or cancelled")
+    p_close.add_argument("--job", required=True)
+    p_close.add_argument("--request", required=True, choices=["deadline_timeout", "cancelled"])
+    p_close.add_argument("--detail", default=None)
+    p_close.add_argument("--expect-dispatch-token", default=None)
+
     p_feedback = sub.add_parser("get-feedback", help="get the last feedback detail (completed/error) for a job")
     p_feedback.add_argument("--job", required=True)
 
@@ -430,6 +439,8 @@ def main(argv: Optional[List[str]] = None) -> int:
             fields["prompt"] = args.prompt
         if args.iteration is not None:
             fields["iteration"] = args.iteration
+        if args.attempt_id is not None:
+            fields["attempt_id"] = args.attempt_id
         if args.role is not None:
             fields["role"] = args.role
         try:
@@ -439,6 +450,47 @@ def main(argv: Optional[List[str]] = None) -> int:
             return 1
         return rc
 
+    if args.command == "close":
+        from lib_py.delegation import engine
+        fields = {}
+        if args.detail is not None:
+            fields["detail"] = args.detail
+
+        if not engine.cas_enabled():
+            req_status = engine.REQUEST_TO_STATUS.get(args.request, "error")
+            fields["status"] = req_status
+            try:
+                mqtt_common.update_job_status(args.job, rd, **fields)
+            except FileNotFoundError as exc:
+                print(str(exc), file=sys.stderr)
+                return 1
+            return 0
+
+        try:
+            res = engine.transition(
+                args.job,
+                args.request,
+                registry_dir=rd,
+                source="delegate_wrapper",
+                fields=fields,
+                expected_dispatch_token=args.expect_dispatch_token,
+            )
+        except FileNotFoundError as exc:
+            print(str(exc), file=sys.stderr)
+            return 1
+
+        if res.committed:
+            return 0
+        if res.idempotent:
+            if res.reason:
+                print(res.reason, file=sys.stderr)
+            return 0
+        if res.reason and "conflicting" in res.reason and "after terminal" in res.reason:
+            print(res.reason, file=sys.stderr)
+            return 0
+        print(f"refused: {res.reason}", file=sys.stderr)
+        return 4
+
     if args.command == "get-feedback":
         print(get_feedback(args.job, rd))
         return 0