fix(codex): resolve peer-review findings R1-R6 and T1-T2

- R1: use herdr send-keys C-c for graceful stop
- R2: preserve JSONL fallback discovery when database is empty
- R3: apply workspace-scoped SQLite query before bounding results
- R4: tighten artifact validation to fail closed on missing/invalid metadata
- R5: verify actual rollout presence before reporting resumable in status
- R6: remove unconditional drift-B backend command fallback
- T1: parameterize artifact metadata regression with verified finder fixture
- T2: seed unmanaged and managed sessions in mock herdr for drift-B testing
- Add final loop review reports (100% PASS)

.agents/skills/multi-agent-mux-monitor/scripts/reconcile.sh

@@ -547,10 +547,6 @@ if herdr_confirmed:
                 except Exception:
                     pass
 
-        if not agent:
-            if pm_check and pm_check.get('cmd') in ('claude', 'agy', 'hermes', 'grok', 'opencode', 'codex'):
-                agent = pm_check['cmd']
-
         if not agent:
             continue