Port · Build: Zed's gpui at 1a28cff

gpui and gpui_platform now come from Zed's repo by git at 1a28cff,
the code gpui-pre 0.3.7 republishes, so the gallery can later build
for the browser. gpui takes stacker, as 0.2.2 always did, and
gpui_platform takes font-kit, without which macOS draws no text;
runtime_shaders moves to gpui_platform.

The API moved: focus, blur and Tab steps take cx, Corner is Anchor,
shaped lines paint with an alignment, defer_draw takes a content
mask, the inspector registers a factory, async updates return their
value, and wrapped lines are shared, not cloned. Updates through a
window context go through the window, so a closed window still ends
them as it did.

Where the new gpui behaves differently, Ely keeps its old intent.
Holds and reveals under a resting pointer survive typing through
gpui's input-modality-independent hover; previews the keyboard also
moves keep the default, and the calendar's leave ignores a key press.
Enter reaches a button inside the code editor, since gpui now arms a
key click on the press. The event logger skips a lone modifier. A
video and an image grid keep their shape in a flex column under
taffy 0.13, as a picture does.

AGENTS.md records the new stack and the rules this port changes; the
rest of the old gpui and taffy rules are re-tested in T44c.

src/shell/tests.rs

@@ -80,7 +80,7 @@ fn the_switcher_switches_on_release_so_its_opener_stays_shut(cx: &mut TestAppCon
         .expect("a managed window");
     });
     settle(cx);
-    cx.update(|window, _| window.focus_next());
+    cx.update(|window, cx| window.focus_next(cx));
     press("enter", cx);
     assert!(desk.read_with(cx, |desk, _| desk.open));
     let above = desk.read_with(cx, |desk, _| desk.enters_above);