Rewrote retro-arcade CSS to properly integrate with marimo's theming:
override all Radix color scales, Tailwind prose vars, and semantic
variables so no dark blue or black text appears on the navy background.
Switched marimo.toml to theme=dark. Added pfs_calcs.py notebook
demonstrating three ways to look up PFS payment rates (carrier file,
RVU calc, pure SQL). Fixed all marimo check warnings/errors across
existing notebooks (branch expressions, empty cells, raw strings).
Added marimo check to pre-commit hook.
3698cd0c63
