docs(plugin-audit): the objects barrel's sys_notification note has an answer now (#4154)

`objects/index.ts` listed `sys_notification` under "Intentionally NOT moved
here" with the reason "reworked by ADR-0030 messaging" — a pending state. The
rework landed and the contribution moved to service-messaging, so the note now
says where it went and why the definition still lives in platform-objects.

Found by the docs-drift check on #4182 flagging plugin-audit. The nine docs it
listed were all verified accurate and need no change — `audit-service.mdx` only
references sys_audit_log/sys_activity, which this plugin still registers.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01L5q3BZMpdiAueHf2emhDY9

Author: claude

packages/plugins/plugin-audit/src/objects/index.ts

@@ -8,7 +8,10 @@
  * @mention hook).
  *
  * Intentionally NOT moved here:
- *   - `sys_notification` — reworked by ADR-0030 messaging.
+ *   - `sys_notification` — the ADR-0030 rework landed, and the object is the
+ *     messaging pipeline's L2 event. Its definition stays in platform-objects,
+ *     and `@objectstack/service-messaging` — the only writer — is what
+ *     contributes it to a kernel (#4154). This plugin no longer registers it.
  *   - `sys_attachment` — a file↔record link belonging with service-storage's
  *     sys_file; stays in platform-objects pending the storage-domain move.
  */