Bug Description

The diagnostics-otel plugin initializes correctly (SDK starts, real Meter/Tracer obtained), but never receives any diagnostic events. This is because the plugin-sdk's event system is disconnected from the core's event emitter.

Root Cause

There are two separate listener sets that are never connected:

1. Core emitter (extensionAPI.js):

   const listeners$3 = /* @__PURE__ */ new Set();
   function emitDiagnosticEvent(event) {
     // ...
     for (const listener of listeners$3) { ... }
   }

2. Plugin SDK (plugin-sdk/index.js):

   const listeners = /* @__PURE__ */ new Set();
   function onDiagnosticEvent(listener) {
     listeners.add(listener);
     return () => listeners.delete(listener);
   }

When the diagnostics-otel plugin calls onDiagnosticEvent() from openclaw/plugin-sdk, it registers to the plugin-sdk's listeners Set. But when the core emits events via emitDiagnosticEvent(), they go to listeners$3 in extensionAPI.js — a completely separate Set.

Steps to Reproduce

1. Configure diagnostics-otel plugin with a working OTLP endpoint (e.g., SigNoz Cloud)
2. Enable diagnostics in config:

   {
     "plugins": { "allow": ["diagnostics-otel"] },
     "diagnostics": {
       "enabled": true,
       "otel": {
         "enabled": true,
         "endpoint": "https://ingest.us.signoz.cloud:443",
         "traces": true,
         "metrics": true,
         "logs": true
       }
     }
   }

3. Restart gateway
4. Generate activity (send messages)
5. Check OTLP backend — no traces or metrics appear

Verification

Added debug logging to the plugin:

diagnostics-otel: SDK started (traces=true, metrics=true)
diagnostics-otel: meter=Meter, tracer=Tracer  // Real, not NoopMeter!
diagnostics-otel: logs exporter enabled (OTLP/HTTP)

But no "received event" logs ever appear — onDiagnosticEvent callback is never called.

Expected Behavior

The plugin-sdk's onDiagnosticEvent should register with the same listener set that the core's emitDiagnosticEvent uses, so plugins receive diagnostic events.

Environment

• OpenClaw version: 2026.2.6-3
• Node: v22.18.0
• OS: macOS (Darwin 24.6.0 arm64)

Suggested Fix

Either:

1. Have plugin-sdk re-export the core's event functions instead of defining separate ones
2. Bridge the two listener sets during plugin initialization
3. Use a shared event bus module imported by both