Update docs Pages workflow to publish on releases with latest-tag default

[nikivanstein]

I implemented (partly using codex) the multi-version documentation we spoke off.
This will help a lot in keeping track of features and releases.

Summary

• Updated .github/workflows/docs2pages.yml triggers to run on both:
  • pushes to main (to keep the main docs variant fresh), and
  • published GitHub releases (to publish on release events).
• Kept sphinx-multiversion as the docs build command.
• Replaced root publishing behavior:
  • instead of always copying main to _site/, the workflow now selects the highest v* version folder (semantic version sort) as the site root default,
  • and only falls back to _site/main when no release-tag folders are present.

Behavior after this change

• main/ docs are still generated and updated.
• The default landing page (/index.html) now points to the latest released tag docs when available.
• New release publication triggers docs deployment immediately.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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