Theme · Platform: one platform for buttons and caps, icon themes, frosted panes

theme::Platform moves out of typography and shell's ControlsStyle folds
into it; the theme's platform starts as the system's. Window buttons Ely
draws, the title bar's layout and every key cap follow it, secondary
included, through typography::keys::keystroke; a title bar whose buttons
the OS draws follows the OS. primitives::IconTheme lays an owner's rules
by file name and extension over Ely's map, for every file icon.
shell::Vibrancy fills a pane with the palette's new glass, translucent
so a window opened Blurred shows its backdrop, solid under high contrast.
gpui 0.2.2 has no Mica; that line stays blocked.

src/lists/directory.rs

@@ -296,7 +296,7 @@ impl RenderOnce for DirectoryListing {
                             Icon::new(if entry.is_folder() {
                                 IconName::Folder
                             } else {
-                                file_icon(&entry.name)
+                                file_icon(&entry.name, cx)
                             })
                             .size(IconSize::Md)
                             .color(colors.fg_muted),