useUp & useDown accept number values but don't support them

[AlfonzAlfonz]

🐛 Bug Report

Hooks useUp & useDown have following type declaration:

declare const useUp: (key: string | number) => boolean;
declare const useDown: (key: string | number) => boolean;

but calling useUp(1024) always returns false.

To Reproduce

const App = () => {
  const upLg = useUp(1024);

  return <>{upLg ? ">lg" : "<lg"}</>
}

Expected behavior

useUp & useDown should either disallow number values or handle them properly.

[quantizor]

Confirmed: useThemeMinValue/useThemeMaxValue look up screens[key], so a numeric value that isn't an actual key in the theme's screens map returns undefined and the hook always reports false. The string | number type signature is misleading; the function only works for breakpoint keys.

Two valid fixes:

1. Narrow key to string (or keyof Screens) so this is a type error at the call site. Smallest change, matches actual behavior.
2. If key is a number, treat it as a literal pixel breakpoint and skip the theme lookup. Bigger change, adds a feature.

I'd lean (1) for the fix and treat (2) as a separate enhancement if anyone wants raw pixel breakpoints. PR welcome.