T00 foundation: theme, motion, assets, icon, buttons, gallery

Theme tokens in light and dark with high contrast, a palette cross-fade,
motion curves and a damped spring, embedded Lucide icons with Inter and
JetBrains Mono, Icon, Button, IconButton, and a gallery that captures
its own window. Reviewed by codex gpt-6-astra (max): PASS in round 3.

examples/gallery/pages/mod.rs

@@ -0,0 +1,19 @@
+mod buttons;
+mod primitives;
+mod theme;
+
+use gpui::{AnyElement, App, Window};
+
+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,
+}
+
+pub const ALL: &[Page] = &[primitives::PAGE, buttons::PAGE, theme::PAGE];
+
+pub fn find(slug: &str) -> Option<usize> {
+    ALL.iter().position(|page| page.slug == slug)
+}