feat: implement HarborForge Monitor OpenClaw Plugin

Architecture:
- openclaw.plugin.json: Plugin manifest with config schema
- index.mjs: Plugin entry, lifecycle hooks (gateway:start/stop)
- sidecar/server.mjs: Independent Node process for telemetry

Features:
- Collects system metrics (CPU, memory, disk, load, uptime)
- Collects OpenClaw status (version, agents)
- HTTP heartbeat to HarborForge Monitor
- Config via ~/.openclaw/openclaw.json
- Sidecar auto-starts/stops with Gateway

Config options:
- enabled, backendUrl, identifier
- challengeUuid (required, from Monitor registration)
- reportIntervalSec, httpFallbackIntervalSec
- logLevel

Provides tool: harborforge_monitor_status

package.json

@@ -0,0 +1,16 @@
+{
+  "name": "harborforge-openclaw-plugin",
+  "version": "0.1.0",
+  "description": "OpenClaw plugin for HarborForge Monitor - streams server telemetry",
+  "type": "module",
+  "main": "index.mjs",
+  "scripts": {
+    "start": "node index.mjs",
+    "sidecar": "node sidecar/server.mjs"
+  },
+  "keywords": ["openclaw", "plugin", "monitoring", "harborforge"],
+  "license": "MIT",
+  "engines": {
+    "node": ">=18.0.0"
+  }
+}