T01 primitives: image, divider, backdrop, focus, pressable, measure, tooltip

Ely-built primitives plus gallery demos for every chapter-one entry,
including gpui natives. The gallery now scripts real input by posting
NSEvents to its own queue and shoots each interaction in both modes.
Codex gpt-6-astra (max): three rounds; the last finding, a two-line
doc comment, was fixed after the three-review cap.

src/lib.rs

@@ -7,18 +7,21 @@ pub mod theme;
 
 pub use assets::Assets;
 
-use gpui::App;
+use gpui::{App, KeyBinding};
 
-use crate::primitives::IconName;
+use crate::primitives::{FocusNext, FocusPrev, IconName};
 
-/// Loads fonts and the theme. Call once, first.
+/// Loads fonts and the theme, binds Tab. Call once, first.
 pub fn init(cx: &mut App) {
-    let probe = IconName::Check.path();
-    let wired = cx.asset_source().load(probe).ok().flatten().is_some();
-    assert!(
-        wired,
-        "ely: pass `ely_gpui_component::Assets` to `Application::with_assets`"
-    );
+    match cx.asset_source().load(IconName::Check.path()) {
+        Ok(Some(_)) => {}
+        Ok(None) => panic!("ely: pass `ely_gpui_component::Assets` to `Application::with_assets`"),
+        Err(error) => panic!("ely: asset source failed: {error:#}"),
+    }
     assets::load_fonts(cx).expect("ely: embedded fonts failed to register");
     theme::Theme::init(cx);
+    cx.bind_keys([
+        KeyBinding::new("tab", FocusNext, None),
+        KeyBinding::new("shift-tab", FocusPrev, None),
+    ]);
 }