Macro cn 

macro_rules! cn {
    ($base:expr, $class:expr $(,)?) => { ... };
    ($($frag:expr),* $(,)?) => { ... };
}

Fuses any number of class fragments into a single String with real Tailwind conflict resolution (like clsx + tailwind-merge): empty fragments drop, the rightmost conflicting utility wins. The TS mirror is cn in @evinvest/uikit.

tw_merge parses every utility in the string on every render, and the overwhelmingly common call is one kit constant plus a caller override that is empty — so that call returns the constant untouched.