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

.agents/skills/multi-agent-mux-create/SKILL.md

@@ -1,7 +1,7 @@
 ---
 name: multi-agent-mux-create
 description: "Create a new agent session (claude, antigravity/agy) in a dedicated herdr session for context-preserving long-running work. Always creates a herdr session — never backgrounds with nohup/disown. Writes the new session to .mam/agent-sessions.yaml. Use when you want to start a fresh agent (no prior UUID) for a new project workspace."
-version: 4.1.3
+version: 4.2.0
 author: godopu
 license: MIT
 platforms: [linux, macos]
@@ -129,7 +129,7 @@ herdr_sessions:
 
 ```bash
 WORKSPACE=/path/to/project
-AGENT=claude  # claude | agy | hermes | grok | opencode — always pass it explicitly
+AGENT=claude  # claude | agy | hermes | grok | opencode | codex — always pass it explicitly
 source .agents/skills/lib.sh
 SESSION_NAME="$(derive_session_name "$WORKSPACE" "$AGENT")"
 
@@ -163,7 +163,10 @@ case "$AGENT" in
   opencode)
     herdr new-session -d -s "$SESSION_NAME" -x 140 -y 40 -c "$WORKSPACE" "opencode --auto --agent build"
     ;;
-  *) echo "ERROR: --agent must be claude, agy, hermes, grok, or opencode, got: $AGENT"; exit 2 ;;
+  codex)
+    herdr new-session -d -s "$SESSION_NAME" -x 140 -y 40 -c "$WORKSPACE" "codex --dangerously-bypass-approvals-and-sandbox"
+    ;;
+  *) echo "ERROR: --agent must be claude, agy, hermes, grok, opencode, or codex, got: $AGENT"; exit 2 ;;
 esac
 
 # 3. Wait for agent TUI to be ready (varies: claude ~5s, agy ~3s)