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/mod.rs

@@ -4,12 +4,16 @@ mod theme;
 
 use gpui::{AnyElement, App, Window};
 
+use crate::script::Step;
+
 pub struct Page {
     pub number: u8,
     pub slug: &'static str,
     pub title: &'static str,
     pub summary: &'static str,
     pub render: fn(&mut Window, &mut App) -> AnyElement,
+    /// Interactions shot after the static pages.
+    pub script: &'static [Step],
 }
 
 pub const ALL: &[Page] = &[primitives::PAGE, buttons::PAGE, theme::PAGE];