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.

README.md

@@ -43,3 +43,4 @@ cargo run --example gallery -- --capture shots   # macOS: PNG of every page, lig
 ## License
 
 MIT or Apache-2.0, at your option. Lucide icons: ISC. Inter and JetBrains Mono: SIL Open Font License 1.1.
+The gallery photos in `examples/gallery/assets` were generated for this project with gpt-image-2.