refactor(plugins): move provider routing metadata to manifests

extensions/mistral/openclaw.plugin.json

@@ -2,6 +2,19 @@
   "id": "mistral",
   "enabledByDefault": true,
   "providers": ["mistral"],
+  "providerEndpoints": [
+    {
+      "endpointClass": "mistral-public",
+      "hosts": ["api.mistral.ai"]
+    }
+  ],
+  "providerRequest": {
+    "providers": {
+      "mistral": {
+        "family": "mistral"
+      }
+    }
+  },
   "providerAuthEnvVars": {
     "mistral": ["MISTRAL_API_KEY"]
   },