Add structured heartbeat responses and Codex tool replies

* Add structured heartbeat response tool

* agents: default codex replies to tools

* agents: use flat heartbeat tool enums

docs/plugins/codex-harness.md

@@ -15,6 +15,17 @@ discovery, native thread resume, native compaction, and app-server execution.
 OpenClaw still owns chat channels, session files, model selection, tools,
 approvals, media delivery, and the visible transcript mirror.
 
+When a source chat turn runs through the Codex harness, visible replies default
+to the OpenClaw `message` tool if the deployment has not explicitly configured
+`messages.visibleReplies`. The agent can still finish its Codex turn privately;
+it only posts to the channel when it calls `message(action="send")`. Set
+`messages.visibleReplies: "automatic"` to keep direct-chat final replies on the
+legacy automatic delivery path.
+
+Codex heartbeat turns also get the `heartbeat_respond` tool by default, so the
+agent can record whether the wake should stay quiet or notify without encoding
+that control flow in final text.
+
 If you are trying to orient yourself, start with
 [Agent runtimes](/concepts/agent-runtimes). The short version is:
 `openai/gpt-5.5` is the model ref, `codex` is the runtime, and Telegram,
@@ -583,7 +594,8 @@ Codex dynamic tools default to the `native-first` profile. In that mode,
 OpenClaw does not expose dynamic tools that duplicate Codex-native workspace
 operations: `read`, `write`, `edit`, `apply_patch`, `exec`, `process`, and
 `update_plan`. OpenClaw integration tools such as messaging, sessions, media,
-cron, browser, nodes, gateway, and `web_search` remain available.
+cron, browser, nodes, gateway, `heartbeat_respond`, and `web_search` remain
+available.
 
 Supported top-level Codex plugin fields: