chore: empty changeset — docs-only PR, releases nothing

Same convention as #4279: the changeset gate wants an explicit statement
of release intent, and skills/ ships in no npm package.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: os-zhuang

.changeset/skills-definehook-examples.md

@@ -0,0 +1,6 @@
+---
+---
+
+docs-only: skills/objectstack-data hook examples author with `defineHook()`
+instead of bare `: Hook` literals, closing the #4269 authoring-validation loop
+on the skill surface (#4274). Releases nothing.