feat: add Tombi schema linting

[rozsazoltan]

Summary

Adds Tombi as the preferred TOML editor and CLI schema validation tool for datarose.toml.

Changes

• Recommend aqua:tombi-toml/tombi through repository-managed mise tooling.
• Add a generated hk.pkl step that runs tombi lint datarose.toml.
• Keep the embedded Rust validator as the required runtime source of truth.
• Format generated schema directives in the Tombi-compatible document header style.
• Update documentation to describe Tombi-based editor and CLI validation.