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.

Cargo.toml

@@ -17,11 +17,13 @@ anyhow = "1"
 gpui = "0.2.2"
 log = "0.4"
 rust-embed = "8.12"
+smallvec = "1"
 
 [dev-dependencies]
 env_logger = "0.11"
 
 [target.'cfg(target_os = "macos")'.dev-dependencies]
+cocoa = "0.26"
 core-foundation = "0.10"
 core-graphics = "0.24"
 image = { version = "0.25", default-features = false, features = ["png"] }