refactor: simplify plugin dependency handling

Simplify plugin installation and runtime loading around package-manager-owned dependencies, with Jiti reserved for local/TS fallback paths.

Also scans npm plugin install roots so hoisted transitive dependencies are covered by dependency denylist and node_modules symlink checks.

extensions/webhooks/package.json

@@ -11,9 +11,6 @@
     "@openclaw/plugin-sdk": "workspace:*"
   },
   "openclaw": {
-    "bundle": {
-      "stageRuntimeDependencies": true
-    },
     "extensions": [
       "./index.ts"
     ]