gpui: Add focus-visible selector support (#40940)

Release Notes:

- N/A

---------

Co-authored-by: Claude <noreply@anthropic.com>

crates/gpui/src/window.rs

@@ -863,6 +863,7 @@ pub struct Window {
     hovered: Rc<Cell<bool>>,
     pub(crate) needs_present: Rc<Cell<bool>>,
     pub(crate) last_input_timestamp: Rc<Cell<Instant>>,
+    last_input_was_keyboard: bool,
     pub(crate) refreshing: bool,
     pub(crate) activation_observers: SubscriberSet<(), AnyObserver>,
     pub(crate) focus: Option<FocusId>,
@@ -1246,6 +1247,7 @@ impl Window {
             hovered,
             needs_present,
             last_input_timestamp,
+            last_input_was_keyboard: false,
             refreshing: false,
             activation_observers: SubscriberSet::new(),
             focus: None,
@@ -1899,6 +1901,12 @@ impl Window {
         self.modifiers
     }
 
+    /// Returns true if the last input event was keyboard-based (key press, tab navigation, etc.)
+    /// This is used for focus-visible styling to show focus indicators only for keyboard navigation.
+    pub fn last_input_was_keyboard(&self) -> bool {
+        self.last_input_was_keyboard
+    }
+
     /// The current state of the keyboard's capslock
     pub fn capslock(&self) -> Capslock {
         self.capslock
@@ -3580,6 +3588,15 @@ impl Window {
     #[profiling::function]
     pub fn dispatch_event(&mut self, event: PlatformInput, cx: &mut App) -> DispatchEventResult {
         self.last_input_timestamp.set(Instant::now());
+
+        // Track whether this input was keyboard-based for focus-visible styling
+        self.last_input_was_keyboard = matches!(
+            event,
+            PlatformInput::KeyDown(_)
+                | PlatformInput::KeyUp(_)
+                | PlatformInput::ModifiersChanged(_)
+        );
+
         // Handlers may set this to false by calling `stop_propagation`.
         cx.propagate_event = true;
         // Handlers may set this to true by calling `prevent_default`.