feat(FN-3714): add WhatsApp chat plugin with plugin discovery and install U

Adds a WhatsApp chat plugin (`plugins/fusion-plugin-whatsapp-chat/`) as the first bundled plugin, including the plugin package with UI rendering, dashboard plugin manager integration, CLI bundling support, and plugin route runtime context. Also updates documentation to cover plugin management and ap

Fusion-Task-Id: FN-3714

plugins/fusion-plugin-whatsapp-chat/package.json

@@ -0,0 +1,31 @@
+{
+  "name": "@fusion-plugin-examples/whatsapp-chat",
+  "version": "0.1.0",
+  "type": "module",
+  "description": "WhatsApp Cloud webhook bridge for Fusion agents",
+  "keywords": [
+    "fusion-plugin",
+    "whatsapp",
+    "chat",
+    "integration"
+  ],
+  "exports": {
+    ".": {
+      "types": "./src/index.ts",
+      "import": "./dist/index.js"
+    }
+  },
+  "private": true,
+  "scripts": {
+    "build": "tsc",
+    "test": "vitest run --silent=passed-only --reporter=dot"
+  },
+  "dependencies": {
+    "@fusion/plugin-sdk": "workspace:*"
+  },
+  "devDependencies": {
+    "@types/node": "^25.5.2",
+    "typescript": "^5.7.0",
+    "vitest": "^3.2.4"
+  }
+}