[hamid-arian]

Summary

• Replaces the temporary release-readiness README with a public user guide.
• Documents the Python 3.0.0 causal API and cross-language scope accurately.
• Corrects supported runtimes, optional dependency groups, installation steps, and contributor commands.

Validation

• Documentation examples executed successfully against the reviewed 3.0.0 source.
• Relative repository links and PyPI-facing absolute links were checked.
• Optional groups match pyproject.toml.
• Attribution, private-path, and local-workspace scans passed.

Release status

This documentation PR does not tag, upload, publish, or release a package.