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.ts

@@ -50,6 +50,30 @@ export class MonitorBridgeClient {
     return this.fetchJson<MonitorTelemetryResponse>('/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: OpenClawMeta): Promise<boolean> {
+    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;
+    }
+  }
+
   private async fetchJson<T>(path: string): Promise<T | null> {
     try {
       const controller = new AbortController();
@@ -67,3 +91,12 @@ export class MonitorBridgeClient {
     }
   }
 }
+
+/**
+ * OpenClaw metadata payload sent to the Monitor bridge.
+ */
+export interface OpenClawMeta {
+  version: string;
+  plugin_version: string;
+  agents?: any[];
+}