feat: add system cli

docs/cli/system.md

@@ -0,0 +1,55 @@
+---
+summary: "CLI reference for `clawdbot system` (system events, heartbeat, presence)"
+read_when:
+  - You want to enqueue a system event without creating a cron job
+  - You need to enable or disable heartbeats
+  - You want to inspect system presence entries
+---
+
+# `clawdbot system`
+
+System-level helpers for the Gateway: enqueue system events, control heartbeats,
+and view presence.
+
+## Common commands
+
+```bash
+clawdbot system event --text "Check for urgent follow-ups" --mode now
+clawdbot system heartbeat enable
+clawdbot system heartbeat last
+clawdbot system presence
+```
+
+## `system event`
+
+Enqueue a system event on the **main** session. The next heartbeat will inject
+it as a `System:` line in the prompt. Use `--mode now` to trigger the heartbeat
+immediately; `next-heartbeat` waits for the next scheduled tick.
+
+Flags:
+- `--text <text>`: required system event text.
+- `--mode <mode>`: `now` or `next-heartbeat` (default).
+- `--json`: machine-readable output.
+
+## `system heartbeat last|enable|disable`
+
+Heartbeat controls:
+- `last`: show the last heartbeat event.
+- `enable`: turn heartbeats back on (use this if they were disabled).
+- `disable`: pause heartbeats.
+
+Flags:
+- `--json`: machine-readable output.
+
+## `system presence`
+
+List the current system presence entries the Gateway knows about (nodes,
+instances, and similar status lines).
+
+Flags:
+- `--json`: machine-readable output.
+
+## Notes
+
+- Requires a running Gateway reachable by your current config (local or remote).
+- System events are ephemeral and not persisted across restarts.