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/layer_shell.rs

@@ -0,0 +1,101 @@
+#![cfg_attr(target_family = "wasm", no_main)]
+
+fn run_example() {
+    #[cfg(all(target_os = "linux", feature = "wayland"))]
+    example::main();
+
+    #[cfg(not(all(target_os = "linux", feature = "wayland")))]
+    panic!("This example requires the `wayland` feature and a linux system.");
+}
+
+#[cfg(not(target_family = "wasm"))]
+fn main() {
+    run_example();
+}
+
+#[cfg(target_family = "wasm")]
+#[wasm_bindgen::prelude::wasm_bindgen(start)]
+pub fn start() {
+    gpui_platform::web_init();
+    run_example();
+}
+
+#[cfg(all(target_os = "linux", feature = "wayland"))]
+mod example {
+    use std::time::{Duration, SystemTime, UNIX_EPOCH};
+
+    use gpui::{
+        App, Bounds, Context, FontWeight, Size, Window, WindowBackgroundAppearance, WindowBounds,
+        WindowKind, WindowOptions, div, layer_shell::*, point, prelude::*, px, rems, rgba, white,
+    };
+    use gpui_platform::application;
+
+    struct LayerShellExample;
+
+    impl LayerShellExample {
+        fn new(cx: &mut Context<Self>) -> Self {
+            cx.spawn(async move |this, cx| {
+                loop {
+                    let _ = this.update(cx, |_, cx| cx.notify());
+                    cx.background_executor()
+                        .timer(Duration::from_millis(500))
+                        .await;
+                }
+            })
+            .detach();
+
+            LayerShellExample
+        }
+    }
+
+    impl Render for LayerShellExample {
+        fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+            let now = SystemTime::now()
+                .duration_since(UNIX_EPOCH)
+                .unwrap()
+                .as_secs();
+
+            let hours = (now / 3600) % 24;
+            let minutes = (now / 60) % 60;
+            let seconds = now % 60;
+
+            div()
+                .size_full()
+                .flex()
+                .items_center()
+                .justify_center()
+                .text_size(rems(4.5))
+                .font_weight(FontWeight::EXTRA_BOLD)
+                .text_color(white())
+                .bg(rgba(0x0000044))
+                .rounded_xl()
+                .child(format!("{:02}:{:02}:{:02}", hours, minutes, seconds))
+        }
+    }
+
+    pub fn main() {
+        application().run(|cx: &mut App| {
+            cx.open_window(
+                WindowOptions {
+                    titlebar: None,
+                    window_bounds: Some(WindowBounds::Windowed(Bounds {
+                        origin: point(px(0.), px(0.)),
+                        size: Size::new(px(500.), px(200.)),
+                    })),
+                    app_id: Some("gpui-layer-shell-example".to_string()),
+                    window_background: WindowBackgroundAppearance::Transparent,
+                    kind: WindowKind::LayerShell(LayerShellOptions {
+                        namespace: "gpui".to_string(),
+                        anchor: Anchor::LEFT | Anchor::RIGHT | Anchor::BOTTOM,
+                        margin: Some((px(0.), px(0.), px(40.), px(0.))),
+                        keyboard_interactivity: KeyboardInteractivity::None,
+                        ..Default::default()
+                    }),
+                    ..Default::default()
+                },
+                |_, cx| cx.new(LayerShellExample::new),
+            )
+            .unwrap();
+        });
+    }
+}