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

tests/test_issue5_phase2b_autocomplete.py

@@ -101,17 +101,16 @@ def test_x03_the_record_carries_iteration_not_an_attempt_id(mam_sandbox, tmp_pat
     """Why auto-completion does not use the engine's expected_attempt.
 
     The engine compares expected_attempt against `attempt_id` falling back to
-    `iteration`. A record has only the latter, and the two mean different things,
-    so the attempt guard is applied where attempt identity actually lives: the
-    dispatch record in the shadow store, compared against observed evidence."""
+    `iteration`. A record now carries attempt_id (initialized to 1 in Issue 6)
+    and iteration, and the attempt guard is applied where attempt identity
+    actually lives: the dispatch record in the shadow store, compared against
+    observed evidence."""
     monkeypatch.chdir(mam_sandbox)
     reg = _reg(tmp_path)
     job_id = _make_job(reg)
     record = _load(reg, job_id)
     assert "iteration" in record
-    assert "attempt_id" not in record, (
-        "if this ever changes, revisit the layering decision in the phase 2b report"
-    )
+    assert record.get("attempt_id") == 1
 
 
 def test_x04_policy_rejects_evidence_from_a_superseded_attempt():