Extract command footer into chrome::command_footer

command_overlay.rs grew past 500 lines after wiring brand glyphs.
Move the footer renderer, the keyboard hint chunks, and the kbd chip
helper into their own module so the overlay file stays under budget
without changing any rendered output.

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

@@ -1,4 +1,5 @@
 pub(crate) mod brand_glyph;
+pub(crate) mod command_footer;
 pub(crate) mod command_overlay;
 pub(crate) mod home;
 pub(crate) mod settings_layout;