docs(protocol): the discovery example's ai entry carries the corrected sentence

The drift check flagged it and a targeted grep found it: http-protocol.mdx's
discovery sample printed the `ai` slot's message as "No implementation ships
for the 'ai' slot" — the line I wrote in #4204, made stale by this PR
correcting the very claim it quotes.

The `workflow` entry beside it is left alone: nothing registers that slot in
either repository, so its sentence is still true.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018UNGqBQcdJ2RYHtWgntJ9B

Author: claude

content/docs/protocol/kernel/http-protocol.mdx

@@ -55,7 +55,7 @@ GET /api/v1/discovery HTTP/1.1
     "metadata": { "enabled": true, "status": "available", "route": "/api/v1/meta", "provider": "objectql" },
     "auth": { "enabled": true, "status": "available", "route": "/api/v1/auth", "provider": "@objectstack/plugin-auth" },
     "workflow": { "enabled": false, "status": "unavailable", "message": "No implementation ships for the 'workflow' slot — register a service under it to enable" },
-    "ai": { "enabled": false, "status": "unavailable", "message": "No implementation ships for the 'ai' slot — register a service under it to enable" }
+    "ai": { "enabled": false, "status": "unavailable", "message": "Provided by @objectstack/service-ai in ObjectStack Cloud/Enterprise — no implementation ships in the open framework" }
   },
   "locale": {
     "default": "en-US",