[Chore] Update TypeScript definitions for React and React DOM

This commit updates the TypeScript definitions for React and React DOM in the skills package from version 18.2.0 to 19.2.3. Additionally, it modifies the SKILL.md file for the Stack Auth skill to specify the code block language as 'text' for better formatting. These changes aim to ensure compatibility with the latest React features and improve documentation clarity.

Author: mantrakp04

apps/skills/package.json

@@ -19,8 +19,8 @@
   },
   "devDependencies": {
     "@types/node": "20.17.6",
-    "@types/react": "^18.2.0",
-    "@types/react-dom": "^18.2.0",
+    "@types/react": "^19.2.3",
+    "@types/react-dom": "^19.2.3",
     "rimraf": "^5.0.5",
     "typescript": "5.9.3"
   }

skills/stack-auth/SKILL.md

@@ -25,7 +25,7 @@ Apply Stack Auth's live instructions — covering user management, auth, payment
 
 Fetch fresh instructions on every invocation:
 
-```
+```text
 https://skill.stack-auth.com
 ```