chore: add changeset for agent skill cleanup (#115)

* fix(sdk): clear removed agent skill bindings

* chore: add changeset for skill binding cleanup

Author: heimanba

.changeset/clear-removed-agent-skills.md

@@ -0,0 +1,7 @@
+---
+"@openagentpack/sdk": patch
+"@openagentpack/cli": patch
+"@openagentpack/playground": patch
+---
+
+Clear stale Bailian and Qoder agent skill bindings when the last declared skill is removed.