fix(generators): mention core-ui-component generator in core-ui template AGENTS.md

The template's AGENTS.md.hbs describes the 4-file component pattern under
`## Structure` but didn't tell agents how to scaffold one. After Phase 4
shipped the generator, an agent reading core-ui's AGENTS.md still wouldn't
discover `pnpm turbo gen core-ui-component` and would build files manually.

Added a one-line note immediately under the Structure heading pointing at
the generator. Snapshot hash for AGENTS.md updated to match.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

turbo/generators/__snapshots__/core-package/ui.snapshot.json

@@ -1,7 +1,7 @@
 [
   {
     "path": "AGENTS.md",
-    "sha256": "ea4a4eeea6cb08364fb7d9cf5c5757147442df1e9b1907b9118fcd313cd1c4a7"
+    "sha256": "626329a8a409b4428307ba0014fb8be179a5db7d1fc2a43b017941ab44476188"
   },
   {
     "path": "eslint.config.js",

turbo/generators/templates/core-package/ui/AGENTS.md.hbs

@@ -44,6 +44,8 @@ import { Modal, Tabs } from "@repo/core-ui";
 
 ## Structure
 
+> To scaffold a new component, use `pnpm turbo gen core-ui-component` rather than creating files manually. The generator emits the 4-file pattern below and splices the export into the tier barrel.
+
 ```
 src/
   atoms/