wayland: fix mouse coordinate scaling for scaled windows

Fix get_mouse_pos to properly convert window coordinates to buffer
coordinates using the scale factor. This resolves buffer bounds errors
in examples like mouse.rs when using Scale::X2, where mouse coordinates
were being reported as window coordinates instead of buffer coordinates.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: emoon

src/os/posix/wayland.rs

@@ -852,8 +852,12 @@ impl Window {
         self.mouse_buttons[index]
     }
 
-    pub fn get_mouse_pos(&self, _mode: MouseMode) -> Option<(f32, f32)> {
-        Some((self.mouse_x, self.mouse_y))
+    pub fn get_mouse_pos(&self, mode: MouseMode) -> Option<(f32, f32)> {
+        let s = self.scale_factor as f32;
+        let w = self.width as f32;
+        let h = self.height as f32;
+
+        mode.get_pos(self.mouse_x, self.mouse_y, s, w, h)
     }
 
     pub fn get_scroll_wheel(&self) -> Option<(f32, f32)> {