feat: reorganize to standard OpenClaw plugin structure

New structure:
├── package.json                 # Root package
├── README.md                    # Documentation
├── plugin/                      # OpenClaw plugin
│   ├── openclaw.plugin.json     # Plugin manifest
│   ├── index.ts                 # Plugin entry (TypeScript)
│   ├── package.json
│   └── tsconfig.json
├── server/                      # Telemetry sidecar
│   └── telemetry.mjs
├── skills/                      # OpenClaw skills
└── scripts/
    └── install.mjs              # Installation script

Matches PaddedCell project structure.
Provides install.mjs with build/install/configure/uninstall commands.

package.json

@@ -3,10 +3,10 @@
   "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"
+    "build": "cd plugin && npm run build",
+    "install": "node scripts/install.mjs",
+    "uninstall": "node scripts/install.mjs --uninstall"
   },
   "keywords": ["openclaw", "plugin", "monitoring", "harborforge"],
   "license": "MIT",