chore(release): sync 9.3.0 metadata

Record the versioned plugin metadata and onboarding docs refreshed by the release preflight so the release workflow can continue from a clean main branch.

plugins/antigravity-bundle-web-designer/.codex-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "antigravity-bundle-web-designer",
-  "version": "9.2.0",
+  "version": "9.3.0",
   "description": "Install the \"Web Designer\" editorial skill bundle from Antigravity Awesome Skills.",
   "author": {
     "name": "sickn33 and contributors",