Windows: fix initial active status (#9694)

Separate from #9451

On Windows, a new window may already active immediate after creation.

Release Notes:

- N/A

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/gpui/src/platform.rs

@@ -188,6 +188,7 @@ pub(crate) trait PlatformWindow: HasWindowHandle + HasDisplayHandle {
         answers: &[&str],
     ) -> Option<oneshot::Receiver<usize>>;
     fn activate(&self);
+    fn is_active(&self) -> bool;
     fn set_title(&mut self, title: &str);
     fn set_edited(&mut self, edited: bool);
     fn show_character_palette(&self);