fix(assets): replace t3code logo with official T3 Code icon (#3326)

Fixes #3325

Agent: code-health

Co-authored-by: B <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Sonnet 4.5 <noreply@anthropic.com>
Co-authored-by: Ahmed Abushagur <ahmed@abushagur.com>

assets/agents/.sources.json

@@ -36,7 +36,7 @@
     "ext": "png"
   },
   "t3code": {
-    "url": "https://avatars.githubusercontent.com/u/59054278?s=200&v=4",
+    "url": "https://t3.codes/icon.png",
     "ext": "png"
   }
 }