docs: finish v0.8.0 documentation rollout

[franciscojavierarceo]

Summary

Make v0.8.0 the default website documentation snapshot and add the missing v0.6.0 and v0.7.0 entries. Each entry points to its verified, immutable tag commit and lists only guide paths present in that snapshot; existing version entries remain intact.

Update the website route documentation and release guide to include the version-manifest step after artifact publication. Remove remaining unpublished-package guidance from the README and docs index, and update the Python documentation test to check published version consistency across the website and install instructions.

Test Plan

• Resolved all three release tags through GitHub and Git and checked each advertised guide path with git ls-tree.
• All repository pre-commit hooks passed.
• All 130 Python tests passed against a locally built 0.8.0 wheel with the full native toolchain; the three documentation tests also passed independently. mkdocs build --strict passed.
• Website build, TypeScript/lint checks, and static checks passed for all 17 pages, including version-specific source links and complete prerender output.