use X/Y instead of W/H in layout widgets

- also core is <2000LoC now yay!
- also using more methods and fewer conditionals

crates/tek_sequencer/src/arranger.rs

@@ -506,7 +506,7 @@ impl<'a> Content for TracksHeader<'a> {
         let Self(_offset, columns, tracks) = *self;
         Split::right(move |add|{
             for (track, (w, _)) in tracks.iter().zip(columns) {
-                add(&Min::W(*w as u16, Layers::new(|add|{
+                add(&Min::X(*w as u16, Layers::new(|add|{
                     add(&FillBg(COLOR_BG1))?;
                     add(&track.name.read().unwrap().as_str())
                 })))?;