• More graceful handling of invalid frontmatter.

• Small cleanups to yaml_util library functions.
• Upgrade ruamel.yaml and build tools.

• Docs and linting fixups

Add support for frontmatter after # comments, for compatibility with shebang and Python inline dependencies.

Migrate to uv build.

More gracefully handle binary files. Support Path args.

Doc updates. Make ruamel.yaml defaults fully customizable for when needed.