feat: push OpenClaw metadata to Monitor bridge periodically

- MonitorBridgeClient gains pushOpenClawMeta() method for POST /openclaw
- OpenClawMeta interface defines version/plugin_version/agents payload
- Plugin pushes metadata on gateway_start (delayed 2s) and periodically
- Interval aligns with reportIntervalSec (default 30s)
- Pushes are non-fatal — plugin continues if Monitor is unreachable
- Interval cleanup on gateway_stop
- Updated monitor-server-connector-plan.md with new architecture

plugin/core/monitor-bridge.js

@@ -23,6 +23,28 @@ class MonitorBridgeClient {
     async telemetry() {
         return this.fetchJson('/telemetry');
     }
+    /**
+     * POST OpenClaw metadata to the Monitor bridge so it can enrich
+     * its heartbeat uploads with OpenClaw version, plugin version,
+     * and agent information.
+     */
+    async pushOpenClawMeta(meta) {
+        try {
+            const controller = new AbortController();
+            const timeout = setTimeout(() => controller.abort(), this.timeoutMs);
+            const response = await fetch(`${this.baseUrl}/openclaw`, {
+                method: 'POST',
+                headers: { 'Content-Type': 'application/json' },
+                body: JSON.stringify(meta),
+                signal: controller.signal,
+            });
+            clearTimeout(timeout);
+            return response.ok;
+        }
+        catch {
+            return false;
+        }
+    }
     async fetchJson(path) {
         try {
             const controller = new AbortController();