fix: Added redirect for prompting guide in examples documentation (#3051)

Forgot to redirect prompting guide for docs. 
    
<!-- This is an auto-generated description by cubic. -->
---

## Summary by cubic
Added a missing docs redirect so /customize/examples/prompting-guide
routes to /customize/agent/prompting-guide. This fixes the broken link
in the Examples docs and prevents 404s.

<!-- End of auto-generated description by cubic. -->

Author: MagMueller

docs/docs.json

@@ -110,6 +110,10 @@
     {
       "source": "/customize/examples/vibetest-use",
       "destination": "/examples/apps/vibetest-use"
+    },
+    {
+      "source": "/customize/examples/prompting-guide",
+      "destination": "/customize/agent/prompting-guide"
     }
   ],
   "navigation": {