logiguard fork: GPUI xdg-activation keyboard-focus serial fix

Single-commit orphan branch: full zed-industries/zed @ 8c74db0 source tree
with a 3-file patch applied (no upstream history).

Patch (crates/gpui_linux/src/linux/wayland/):
  - serial.rs: add SerialKind::KeyboardEnter
  - client.rs: store wl_keyboard.enter serial; add latest_serial_of()
  - window.rs: activate() uses keyboard-enter serial (Mutter focus gate)

Mutter honors window activation only when the token carries the keyboard-
focus serial from wl_keyboard.enter; GPUI used a stale mouse-press serial.
See docs/tray-window-focus-wayland.md in logiguard.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

crates/gpui/examples/gif_viewer.rs

@@ -0,0 +1,56 @@
+#![cfg_attr(target_family = "wasm", no_main)]
+
+use gpui::{App, Context, Render, Window, WindowOptions, div, img, prelude::*};
+use gpui_platform::application;
+use std::path::PathBuf;
+
+struct GifViewer {
+    gif_path: PathBuf,
+}
+
+impl GifViewer {
+    fn new(gif_path: PathBuf) -> Self {
+        Self { gif_path }
+    }
+}
+
+impl Render for GifViewer {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        div().size_full().child(
+            img(self.gif_path.clone())
+                .size_full()
+                .object_fit(gpui::ObjectFit::Contain)
+                .id("gif"),
+        )
+    }
+}
+
+fn run_example() {
+    application().run(|cx: &mut App| {
+        let gif_path =
+            PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("examples/image/black-cat-typing.gif");
+
+        cx.open_window(
+            WindowOptions {
+                focus: true,
+                ..Default::default()
+            },
+            |_, cx| cx.new(|_| GifViewer::new(gif_path)),
+        )
+        .unwrap();
+        cx.activate(true);
+    });
+}
+
+#[cfg(not(target_family = "wasm"))]
+fn main() {
+    env_logger::init();
+    run_example();
+}
+
+#[cfg(target_family = "wasm")]
+#[wasm_bindgen::prelude::wasm_bindgen(start)]
+pub fn start() {
+    gpui_platform::web_init();
+    run_example();
+}