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/project/src/debounced_delay.rs

@@ -0,0 +1,54 @@
+use futures::{FutureExt, channel::oneshot};
+use gpui::{Context, Task};
+use std::{marker::PhantomData, time::Duration};
+
+pub struct DebouncedDelay<E: 'static> {
+    task: Option<Task<()>>,
+    cancel_channel: Option<oneshot::Sender<()>>,
+    _phantom_data: PhantomData<E>,
+}
+
+impl<E: 'static> Default for DebouncedDelay<E> {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+impl<E: 'static> DebouncedDelay<E> {
+    pub fn new() -> Self {
+        Self {
+            task: None,
+            cancel_channel: None,
+            _phantom_data: PhantomData,
+        }
+    }
+
+    pub fn fire_new<F>(&mut self, delay: Duration, cx: &mut Context<E>, func: F)
+    where
+        F: 'static + Send + FnOnce(&mut E, &mut Context<E>) -> Task<()>,
+    {
+        if let Some(channel) = self.cancel_channel.take() {
+            _ = channel.send(());
+        }
+
+        let (sender, mut receiver) = oneshot::channel::<()>();
+        self.cancel_channel = Some(sender);
+
+        let previous_task = self.task.take();
+        self.task = Some(cx.spawn(async move |entity, cx| {
+            let mut timer = cx.background_executor().timer(delay).fuse();
+            if let Some(previous_task) = previous_task {
+                previous_task.await;
+            }
+
+            futures::select_biased! {
+                _ = receiver => return,
+                _ = timer => {}
+            }
+
+            if let Ok(task) = entity.update(cx, |project, cx| (func)(project, cx)) {
+                task.await;
+            }
+        }));
+    }
+}