Bump workers-ai-provider to v3.1.5

Update workers-ai-provider from ^3.1.4 to ^3.1.5 in package.json and update package-lock.json to match. This is a dependency version bump to pick up the latest patch release.

Author: threepointone

package-lock.json

@@ -28,7 +28,7 @@
     "react": "^19.2.4",
     "react-dom": "^19.2.4",
     "streamdown": "^2.2.0",
-    "workers-ai-provider": "^3.1.4",
+    "workers-ai-provider": "^3.1.5",
     "zod": "^4.3.6"
   },
   "devDependencies": {