Summary

• Extracts the Sphinx + JupyterLite build/deploy steps out of ci.yml into a workflow_call reusable workflow (docs.yml), so the logic lives in one place.
• Adds docs-publish.yml, a workflow_dispatch-only entry point that calls the same docs.yml steps without waiting on the full OS/Python test matrix — useful for a docs-only fix that doesn't need the whole suite to re-run first.
• ci.yml behavior is unchanged: its docs job still runs only after test-core/test pass, just delegates to docs.yml instead of duplicating the steps.
• Deployment to GitHub Pages still only happens when run against main (checked inside docs.yml's docs-deploy job), so a manual dispatch from another branch just builds, it doesn't publish.

Test plan

• Confirm ci.yml still builds + deploys docs on a push to main, same as before
• Manually dispatch "Docs Publish (manual)" from the Actions tab against main and confirm it builds and deploys the site
• Manually dispatch it from a non-main branch and confirm it builds but does not attempt to deploy