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/grid_layout.rs

@@ -0,0 +1,94 @@
+#![cfg_attr(target_family = "wasm", no_main)]
+
+use gpui::{
+    App, Bounds, Context, Hsla, Window, WindowBounds, WindowOptions, div, prelude::*, px, rgb, size,
+};
+use gpui_platform::application;
+
+// https://en.wikipedia.org/wiki/Holy_grail_(web_design)
+struct HolyGrailExample {}
+
+impl Render for HolyGrailExample {
+    fn render(&mut self, _window: &mut Window, _cx: &mut Context<Self>) -> impl IntoElement {
+        let block = |color: Hsla| {
+            div()
+                .size_full()
+                .bg(color)
+                .border_1()
+                .border_dashed()
+                .rounded_md()
+                .border_color(gpui::white())
+                .items_center()
+        };
+
+        div()
+            .gap_1()
+            .grid()
+            .bg(rgb(0x505050))
+            .size(px(500.0))
+            .shadow_lg()
+            .border_1()
+            .size_full()
+            .grid_cols(5)
+            .grid_rows(5)
+            .child(
+                block(gpui::white())
+                    .row_span(1)
+                    .col_span_full()
+                    .child("Header"),
+            )
+            .child(
+                block(gpui::red())
+                    .col_span(1)
+                    .h_56()
+                    .child("Table of contents"),
+            )
+            .child(
+                block(gpui::green())
+                    .col_span(3)
+                    .row_span(3)
+                    .child("Content"),
+            )
+            .child(
+                block(gpui::blue())
+                    .col_span(1)
+                    .row_span(3)
+                    .child("AD :(")
+                    .text_color(gpui::white()),
+            )
+            .child(
+                block(gpui::black())
+                    .row_span(1)
+                    .col_span_full()
+                    .text_color(gpui::white())
+                    .child("Footer"),
+            )
+    }
+}
+
+fn run_example() {
+    application().run(|cx: &mut App| {
+        let bounds = Bounds::centered(None, size(px(500.), px(500.0)), cx);
+        cx.open_window(
+            WindowOptions {
+                window_bounds: Some(WindowBounds::Windowed(bounds)),
+                ..Default::default()
+            },
+            |_, cx| cx.new(|_| HolyGrailExample {}),
+        )
+        .unwrap();
+        cx.activate(true);
+    });
+}
+
+#[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();
+}