fix(agent-author): require plugin version bump after agent changes

## Why
Same gap as skill-author: no instruction to bump the plugin version after
creating or modifying an agent inside a plugin.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

plugins/kyberforge/plugin.json

@@ -13,5 +13,5 @@
   "skills": [
     "skills/"
   ],
-  "version": "1.0.4"
+  "version": "1.0.5"
 }