ci(docs[trigger]): publish from seo-packages branch

why: the docs workflow currently triggers on pushes to main only,
which means the seo-packages branch cannot exercise the publish
pipeline (uv sync → just html → S3 sync → CloudFront invalidate →
Cloudflare purge) end-to-end. Adding seo-packages to the on.push
branches list lets a single push validate the entire pipeline
without merging to main first. The dorny/paths-filter step still
gates the publish to docs-relevant changes, so unrelated pushes
still skip.

what:
- .github/workflows/docs.yml: append seo-packages to the
  on.push.branches list so the workflow runs on pushes to either
  branch

Author: tony

.github/workflows/docs.yml

@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - main
+      - seo-packages
 
 permissions:
   contents: read