feat(agent): add full codex agent support (v4.2.0)

- Implement CodexAdapter in lib_py/agents/adapters/codex.py with safe flags and TUI readiness
- Extend create_session, resume_session, stop_session, and reconcile for codex CLI
- Support codex agent delegation and loop integration across all multi-agent skills
- Add unit, component, and contract test suites for codex integration
- Verify all 462 tests passing cleanly

tests/test_tier2_component.py

@@ -1276,3 +1276,53 @@ def test_comp_opencode_create_and_reconcile_and_stop(mam_sandbox, mock_herdr, mo
     assert s_stopped["resumable"] is True
 
 
+def test_comp_codex_create_and_reconcile_and_stop(mam_sandbox, mock_herdr, mock_agents):
+    """Verify create_session -> reconcile drift-C materialization -> stop flow for codex."""
+    create_script = mam_sandbox / ".agents" / "skills" / "multi-agent-mux-create" / "scripts" / "create_session.sh"
+    res = subprocess.run([
+        "bash", str(create_script),
+        "--workspace", str(mam_sandbox),
+        "--agent", "codex",
+        "--role", "creator"
+    ], capture_output=True, text=True, cwd=str(mam_sandbox))
+    assert res.returncode == 0, res.stderr
+
+    yaml_path = mam_sandbox / ".mam" / "agent-sessions.yaml"
+    import yaml
+    with open(yaml_path) as f:
+        data = yaml.safe_load(f)
+    sessions = data.get("herdr_sessions", [])
+    assert len(sessions) == 1
+    s = sessions[0]
+    session_name = s["name"]
+    assert s["status"] == "running"
+    assert s["codex_session_id_own"] is None
+    assert s["session_id_source"] == "pending-discovery"
+
+    # Run reconcile.sh to trigger drift-C materialization
+    reconcile_script = mam_sandbox / ".agents" / "skills" / "multi-agent-mux-monitor" / "scripts" / "reconcile.sh"
+    res_rec = subprocess.run(["bash", str(reconcile_script), "--once", "--emit-diff"], capture_output=True, text=True, cwd=str(mam_sandbox), env={**os.environ, "WORKSPACE_ROOT": str(mam_sandbox)})
+    assert res_rec.returncode == 0, res_rec.stderr
+
+    with open(yaml_path) as f:
+        data_after = yaml.safe_load(f)
+    s_after = [x for x in data_after.get("herdr_sessions", []) if x.get("name") == session_name][0]
+    assert s_after.get("codex_session_id_own") is not None
+    assert s_after.get("last_visible_status") in ("pinned", "resume_verified")
+
+    # Stop session
+    stop_script = mam_sandbox / ".agents" / "skills" / "multi-agent-mux-stop" / "scripts" / "stop_session.sh"
+    res_stop = subprocess.run([
+        "bash", str(stop_script),
+        "--session", session_name,
+        "--agent", "codex"
+    ], capture_output=True, text=True, cwd=str(mam_sandbox))
+    assert res_stop.returncode == 0, res_stop.stderr
+
+    with open(yaml_path) as f:
+        data_stopped = yaml.safe_load(f)
+    s_stopped = [x for x in data_stopped.get("herdr_sessions", []) if x.get("name") == session_name][0]
+    assert s_stopped["status"] == "stopped"
+    assert s_stopped["resumable"] is True
+
+