ci(docs): trigger Pages deploy on main pushes instead of tags

Tag pushes were rejected by the github-pages environment protection
rules. Releases land on main via release-please, so triggering on main
both fixes the deploy and keeps docs in sync with shipped code.

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

Author: gjtorikian

.github/workflows/docs.yml

@@ -1,7 +1,7 @@
 name: Publish API Docs
 on:
   push:
-    tags: ['v*']
+    branches: [main]
   workflow_dispatch:
 permissions:
   contents: read