fix: use caduceus ⚕ icon for hermes agent (#2181)

Replace the Nous Research org avatar with the actual Staff of Hermes
(⚕) symbol from the hermes-agent page favicon. Sourced from the
WordPress emoji SVG and converted to 180x180 PNG.

Co-authored-by: lab <6723574+louisgv@users.noreply.github.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

assets/agents/.sources.json

@@ -24,7 +24,7 @@
     "ext": "png"
   },
   "hermes": {
-    "url": "https://avatars.githubusercontent.com/u/100869521?s=200&v=4",
+    "url": "https://s.w.org/images/core/emoji/17.0.2/svg/2695.svg",
     "ext": "png"
   }
 }