Now with a command line!

This adds an initial LensKit command-line utility and some small quality-of-life bits.

What's Changed

• Add utility function to load seeds from configuration files by @mdekstrand in #625
• Add Markdown dataset statistics by @mdekstrand in #626
• Add LensKit CLI tool and move data tools into it by @mdekstrand in #627

Full Changelog: v2025.1.1b5...v2025.1.1b6