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/ui/src/styles/spacing.rs

@@ -0,0 +1,54 @@
+use gpui::{App, Pixels, Rems, px, rems};
+use theme::UiDensity;
+use ui_macros::derive_dynamic_spacing;
+
+// Derives [DynamicSpacing]. See [ui_macros::derive_dynamic_spacing].
+//
+// There are 3 UI density settings: Compact, Default, and Comfortable.
+//
+// When a tuple of three values is provided, the values are used directly.
+//
+// Example: (1, 2, 4) => Compact: 1px, Default: 2px, Comfortable: 4px
+//
+// When a single value is provided, the standard spacing formula is
+// used to derive the of spacing values. This formula can be found in
+// the macro.
+//
+// Example:
+//
+// Assuming the standard formula is (n-4, n, n+4)
+//
+// 24 => Compact: 20px, Default: 24px, Comfortable: 28px
+//
+// The [DynamicSpacing] enum variants use a BaseXX format,
+// where XX = the pixel value @ default rem size and the default UI density.
+//
+// Example:
+//
+// DynamicSpacing::Base16 would return 16px at the default UI scale & density.
+derive_dynamic_spacing![
+    (0, 0, 0),
+    (1, 1, 2),
+    (1, 2, 4),
+    (2, 3, 4),
+    (2, 4, 6),
+    (3, 6, 8),
+    (4, 8, 10),
+    (10, 12, 14),
+    (14, 16, 18),
+    (18, 20, 22),
+    24,
+    32,
+    40,
+    48
+];
+
+/// Returns the current [`UiDensity`] setting. Use this to
+/// modify or show something in the UI other than spacing.
+///
+/// Do not use this to calculate spacing values.
+///
+/// Always use [DynamicSpacing] for spacing values.
+pub fn ui_density(cx: &mut App) -> UiDensity {
+    theme::theme_settings(cx).ui_density(cx)
+}