docs(release): clarify PyPI publisher binding and automatic release

[Si40Code]

Summary

• Document that the pypi environment no longer requires separate deployment approval, as explicitly requested by the maintainer.
• Preserve OIDC publishing and main/v* deployment restrictions.
• Explain the exact existing-project Trusted Publisher binding and safe recovery from invalid-publisher.

Incident

Release run 35843079307 passed the build but PyPI rejected the OIDC exchange with invalid-publisher. This documentation change does not by itself fix the external PyPI project configuration. That configuration must match CALLE-AI / server-sdk-python / publish-python.yml / pypi before retrying the failed publish job.

Validation

• Documentation-only change; git diff --check passed.
• No package, generated contract, runtime or dependency change.