T26a Media: images

A new chapter, src/media. ImageViewer fits a picture to its stage and
zooms by the document steps, by keys, buttons and Cmd-scroll about the
pointer; a drag through gpui's drag, a scroll or the arrows pan it once it
overhangs; R turns it a quarter at a time. gpui paints pictures without a
transform, so media::turn turns the decoded frames off the main thread,
an asset keyed by the picture and the turn; `image` 0.25, which gpui
already decodes with, is now a dependency. ImageThumbnail shows a picture
in its own shape with a corner label and a ring when chosen, and is a Tab
stop only with a handler. Lightbox / Gallery Viewer points to
overlays::Lightbox, which the gallery opens from the thumbnails.

T26 splits into T26a–e. AGENTS.md: the drag rule says drags that pan,
turn or slide go through gpui's drag; pictures turn by their pixels.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

examples/gallery/pages/media/mod.rs

@@ -0,0 +1,40 @@
+mod images;
+
+use gpui::{AnyElement, App, IntoElement, ParentElement, Window, div};
+
+use super::Page;
+use crate::script::Step;
+
+pub const PAGE: Page = Page {
+    number: 26,
+    slug: "media",
+    title: "Media",
+    summary: "Pictures, video and sound: looking closely, cropping and marking up, playing, and the controls and devices around them.",
+    render,
+    script: SCRIPT,
+};
+
+const SCRIPT: &[Step] = &[
+    Step::DownAt("media-viewer", 320.0, 240.0),
+    Step::UpAt("media-viewer", 320.0, 240.0),
+    Step::Key("="),
+    Step::Key("="),
+    Step::Wait(300),
+    Step::Shot("zoomed"),
+    Step::Key("r"),
+    Step::Wait(500),
+    Step::Shot("turned"),
+    Step::DownAt("media-thumbs", 237.0, 50.0),
+    Step::UpAt("media-thumbs", 237.0, 50.0),
+    Step::Wait(500),
+    Step::Shot("lightbox"),
+    Step::Key("escape"),
+    Step::Wait(300),
+];
+
+fn render(window: &mut Window, cx: &mut App) -> AnyElement {
+    div()
+        .child(images::viewer(cx))
+        .child(images::thumbnails(window, cx))
+        .into_any_element()
+}