Match Continue card column ratio + add Cmd+K omnibar focus

- Continue card: switch from grid_cols(2) (50/50) to flex with a
  flex-1 history column and a fixed 240 px reading-list cover, matching
  the design's grid-template-columns: 1fr 240px.
- Cmd+K (Ctrl+K on Windows/Linux) now aliases FocusAddressBar so the
  ⌘K affordance shown in Arc/Dia/Linear-style designs lands on the
  omnibar without disturbing the existing Cmd+L mapping.

crates/ely_app/src/shortcuts.rs

@@ -204,7 +204,9 @@ pub(crate) const SHORTCUT_BINDINGS: &[ShortcutBinding] = &[
     shortcut(ShortcutAction::OpenSettings, ShortcutPlatform::Macos, "cmd-,"),
     shortcut(ShortcutAction::OpenSettings, ShortcutPlatform::WindowsLinux, "ctrl-,"),
     shortcut(ShortcutAction::FocusAddressBar, ShortcutPlatform::Macos, "cmd-l"),
+    shortcut(ShortcutAction::FocusAddressBar, ShortcutPlatform::Macos, "cmd-k"),
     shortcut(ShortcutAction::FocusAddressBar, ShortcutPlatform::WindowsLinux, "ctrl-l"),
+    shortcut(ShortcutAction::FocusAddressBar, ShortcutPlatform::WindowsLinux, "ctrl-k"),
     shortcut(ShortcutAction::CloseCurrentTab, ShortcutPlatform::Macos, "cmd-w"),
     shortcut(ShortcutAction::CloseCurrentTab, ShortcutPlatform::WindowsLinux, "ctrl-w"),
     shortcut(ShortcutAction::RestoreClosedTab, ShortcutPlatform::Macos, "cmd-shift-t"),