Track xy (Reflex's Rust charting library) for possible inclusion

[tdhopper]

https://reflex.dev/blog/xy-python-charting-library/

As of Aug 2026: v0.0.5, self-described experimental, interactive HTML/GPU output with no documented static-image export, 2D basics only.

Revisit when it has: (1) a stable release, (2) PNG/static export usable from a notebook cell, (3) enough API surface to cover roughly the rows classic seaborn covers (facets, regression, KDE, box, heatmap). The site's build requires image/png in cell outputs; see CLAUDE.md.