Migrate Tailwind to StyleX

Convert Tailwind utility classes into StyleX styles: replace className="..." strings with entries in a stylex.create({...}) call, and apply them with stylex.props(...).

This is a behavior-preserving refactor, not a redesign. The rendered pixels should not change. Don't drop styles you can't cleanly convert — flag them (see Step 6) so the user can decide, rather than silently changing the design.

The core mechanic: resolve, then reshape

The reliable way to convert a class string is the same one the tw-to-stylex codemod uses under the hood: resolve each class to the CSS it actually produces, then reshape that CSS into a StyleX object. Don't pattern-match class names to guesses — think in the computed CSS, because that's what has to stay identical.