gpui: Don’t hide Window in docs (#25449)

Release Notes:

- N/A

This side effect is only appearing in outside project.

## Before

<img width="414" alt="image"
src="https://github.com/user-attachments/assets/73d215d2-20e4-4337-82f4-74daa88a1bae"
/>

## After

<img width="453" alt="image"
src="https://github.com/user-attachments/assets/030d34d7-c425-44f6-9cc5-0f2f6fd0a1ac"
/>

---------

Co-authored-by: Marshall Bowers <git@maxdeviant.com>

crates/gpui/src/window.rs

@@ -593,8 +593,7 @@ impl Frame {
     }
 }
 
-// Holds the state for a specific window.
-#[doc(hidden)]
+/// Holds the state for a specific window.
 pub struct Window {
     pub(crate) handle: AnyWindowHandle,
     pub(crate) invalidator: WindowInvalidator,
@@ -1007,6 +1006,7 @@ impl Window {
         subscription
     }
 
+    /// Replaces the root entity of the window with a new one.
     pub fn replace_root<E>(
         &mut self,
         cx: &mut App,
@@ -1021,6 +1021,7 @@ impl Window {
         view
     }
 
+    /// Returns the root entity of the window, if it has one.
     pub fn root<E>(&self) -> Option<Option<Entity<E>>>
     where
         E: 'static + Render,