ci: let workflow_dispatch actually deploy docs, rename to "Docs Publish"

[petercorke]

Summary

• docs.yml already listed workflow_dispatch as a trigger, but the upload-pages-artifact step and the deploy job were both gated on github.event_name == 'push' — a manual run silently built the docs and threw the result away without publishing. Widens both guards to also allow workflow_dispatch.
• Adds an explicit github.ref == 'refs/heads/main' check on deploy, since workflow_dispatch (unlike push, already restricted via branches: [main]) can be run against any branch — a manual dispatch from a feature branch now builds but doesn't publish.
• Renames the workflow from "Docs" to "Docs Publish" to match the same button name across RTB/bdsim.

Test plan

• Push to main still builds + deploys docs, same as before
• A PR still triggers a build-only run (no artifact upload, no deploy)
• Manually dispatch "Docs Publish" against main and confirm it now actually deploys
• Manually dispatch it from a non-main branch and confirm it builds but does not deploy

[codacy-production]

Up to standards ✅

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