Remove broken sidebar Layout cards from appearance settings

The three layout preset cards (Single column / Compact / Hidden on
hover) painted as bright white boxes regardless of theme, never
implemented the layouts they previewed, and duplicated the live
sidebar resize handle which already covers the same intent. Drop
the section, the supporting `appearance_layout_cards` module, and
the chrome `mod` declaration that re-exported it.

crates/ely_app/src/shell/chrome/mod.rs

@@ -1,6 +1,5 @@
 pub(crate) mod animations;
 pub(crate) mod appearance_form;
-pub(crate) mod appearance_layout_cards;
 pub(crate) mod brand_glyph;
 pub(crate) mod command_footer;
 pub(crate) mod command_match;