Align Rust, TypeScript and Python versions and both landing-page notes.
Document protocol validation, mailbox recovery and the latest relay fixes
since v0.12.5, including integration requirements.

Validation: make test (including Mail interoperability), pnpm -r build,
version/metadata consistency checks, and bilingual landing-page/demo checks.

Co-authored-by: Codex <codex@openai.com>