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/language_selector/src/active_buffer_language.rs

@@ -0,0 +1,98 @@
+use editor::Editor;
+use gpui::{
+    App, Context, Entity, IntoElement, ParentElement, Render, Styled, Subscription, WeakEntity,
+    Window, div,
+};
+use language::LanguageName;
+use settings::Settings as _;
+use ui::{Button, ButtonCommon, Clickable, FluentBuilder, LabelSize, Tooltip};
+use workspace::{HideStatusItem, StatusBarSettings, StatusItemView, Workspace, item::ItemHandle};
+
+use crate::{LanguageSelector, Toggle};
+
+pub struct ActiveBufferLanguage {
+    active_language: Option<Option<LanguageName>>,
+    workspace: WeakEntity<Workspace>,
+    _observe_active_editor: Option<Subscription>,
+}
+
+impl ActiveBufferLanguage {
+    pub fn new(workspace: &Workspace) -> Self {
+        Self {
+            active_language: None,
+            workspace: workspace.weak_handle(),
+            _observe_active_editor: None,
+        }
+    }
+
+    fn update_language(&mut self, editor: Entity<Editor>, _: &mut Window, cx: &mut Context<Self>) {
+        self.active_language = Some(None);
+
+        let editor = editor.read(cx);
+        if let Some(buffer) = editor.active_buffer(cx)
+            && let Some(language) = buffer.read(cx).language()
+        {
+            self.active_language = Some(Some(language.name()));
+        }
+
+        cx.notify();
+    }
+}
+
+impl Render for ActiveBufferLanguage {
+    fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
+        if !StatusBarSettings::get_global(cx).active_language_button {
+            return div().hidden();
+        }
+
+        div().when_some(self.active_language.as_ref(), |el, active_language| {
+            let active_language_text = if let Some(active_language_text) = active_language {
+                active_language_text.to_string()
+            } else {
+                "Unknown".to_string()
+            };
+
+            el.child(
+                Button::new("change-language", active_language_text)
+                    .label_size(LabelSize::Small)
+                    .on_click(cx.listener(|this, _, window, cx| {
+                        if let Some(workspace) = this.workspace.upgrade() {
+                            workspace.update(cx, |workspace, cx| {
+                                LanguageSelector::toggle(workspace, window, cx)
+                            });
+                        }
+                    }))
+                    .tooltip(|_window, cx| Tooltip::for_action("Select Language", &Toggle, cx)),
+            )
+        })
+    }
+}
+
+impl StatusItemView for ActiveBufferLanguage {
+    fn set_active_pane_item(
+        &mut self,
+        active_pane_item: Option<&dyn ItemHandle>,
+        window: &mut Window,
+        cx: &mut Context<Self>,
+    ) {
+        if let Some(editor) = active_pane_item.and_then(|item| item.downcast::<Editor>()) {
+            self._observe_active_editor =
+                Some(cx.observe_in(&editor, window, Self::update_language));
+            self.update_language(editor, window, cx);
+        } else {
+            self.active_language = None;
+            self._observe_active_editor = None;
+        }
+
+        cx.notify();
+    }
+
+    fn hide_setting(&self, _: &App) -> Option<HideStatusItem> {
+        Some(HideStatusItem::new(|settings| {
+            settings
+                .status_bar
+                .get_or_insert_default()
+                .active_language_button = Some(false);
+        }))
+    }
+}