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.

examples/gallery/pages/theme.rs

@@ -18,6 +18,7 @@ pub const PAGE: Page = Page {
     title: "Theme",
     summary: "Tokens every component reads. Light and dark share one grammar.",
     render,
+    script: &[],
 };
 
 fn render(_: &mut Window, cx: &mut App) -> AnyElement {