Fix AccessKit node bounds (#18706)

# Objective

Fixes #18685

## Solution

* Don't apply the camera translation.
* Calculate the min and max bounds of the accessibility node rect taking
the UI translation relative to its center not the top-left corner.

## Testing

Install [NVDA](https://www.nvaccess.org/). In NVDA set `Preferences ->
Settings -> Vision -> Enable Highlighting`.

Then run bevy's `tab_navigation` example:
```
cargo run --example tab_navigation
```
If everything is working correctly, NVDA should draw a border around the
currently selected tab button:

![Screenshot 2025-04-07
130523](https://github.com/user-attachments/assets/07d9a795-5d55-4b61-9602-2e8917020245)

Author: ickshonpe

crates/bevy_ui/src/accessibility.rs

@@ -13,7 +13,8 @@ use bevy_ecs::{
     system::{Commands, Query},
     world::Ref,
 };
-use bevy_render::{camera::CameraUpdateSystem, prelude::Camera};
+use bevy_math::Vec3Swizzles;
+use bevy_render::camera::CameraUpdateSystem;
 use bevy_transform::prelude::GlobalTransform;
 
 use accesskit::{Node, Rect, Role};
@@ -36,28 +37,20 @@ fn calc_label(
 }
 
 fn calc_bounds(
-    camera: Query<(&Camera, &GlobalTransform)>,
     mut nodes: Query<(
         &mut AccessibilityNode,
         Ref<ComputedNode>,
         Ref<GlobalTransform>,
     )>,
 ) {
-    if let Ok((camera, camera_transform)) = camera.single() {
-        for (mut accessible, node, transform) in &mut nodes {
-            if node.is_changed() || transform.is_changed() {
-                if let Ok(translation) =
-                    camera.world_to_viewport(camera_transform, transform.translation())
-                {
-                    let bounds = Rect::new(
-                        translation.x.into(),
-                        translation.y.into(),
-                        (translation.x + node.size.x).into(),
-                        (translation.y + node.size.y).into(),
-                    );
-                    accessible.set_bounds(bounds);
-                }
-            }
+    for (mut accessible, node, transform) in &mut nodes {
+        if node.is_changed() || transform.is_changed() {
+            let center = transform.translation().xy();
+            let half_size = 0.5 * node.size;
+            let min = center - half_size;
+            let max = center + half_size;
+            let bounds = Rect::new(min.x as f64, min.y as f64, max.x as f64, max.y as f64);
+            accessible.set_bounds(bounds);
         }
     }
 }