Phase 9: retract vet as a standalone repo in the docs hub

- removed the vet entry from config.yml (port 8013) and repos.json (13 -> 12)
- dropped the collected vet/ site output (lib + mcp); collect.py no longer
  emits it
- inventory, drone and UI docs no longer list vet; the reference app now
  lives only inside standards (src/templates + the wiki walkthrough)
- homepage/_index refreshed

react/vet itself is deleted in a later phase (after .run configs land).

_index/index.html

@@ -106,13 +106,6 @@
       <a href="/khata-app/lib/" target="_blank">view lib</a>
     </div>
   </div>
-  <div class="card">
-    <h3>Vet</h3>
-    <p>Full-stack reference application — OpenAPI-first FastAPI server paired with the spec-driven React admin client (@aetoskia/react-openapi + @aetoskia/react-auth).</p>
-    <div class="card-actions">
-      <a href="/vet/lib/" target="_blank">view lib</a>
-    </div>
-  </div>
 </div>
 </section>