gpui: Support disabling window resizing and minimizing (#36859)

Add support to disable both window resizing and minimizing.

| | macOS | Windows |
| - | - | - |
| **Unresizable** | <img width="412" height="440"
alt="SCR-20250822-qpea"
src="https://github.com/user-attachments/assets/d6d45510-dc4b-436f-a9fa-ce9cb0b0c411"
/> | <img width="276" height="298" alt="2025-08-22 110757"
src="https://github.com/user-attachments/assets/9deff498-e903-4173-9c26-072dd9409fc1"
/> |
| **Unminimizable** | <img width="412" height="440"
alt="SCR-20250822-qpfl"
src="https://github.com/user-attachments/assets/e1d5f9eb-6de5-4908-8b52-38ccb2e65689"
/> | <img width="276" height="298" alt="2025-08-22 110814"
src="https://github.com/user-attachments/assets/da94b006-3544-4274-8b02-1cab7ca8dd70"
/> |

Release Notes:

- N/A

crates/gpui/src/platform/mac/window.rs

@@ -530,6 +530,8 @@ impl MacWindow {
             titlebar,
             kind,
             is_movable,
+            is_resizable,
+            is_minimizable,
             focus,
             show,
             display_id,
@@ -545,10 +547,16 @@ impl MacWindow {
 
             let mut style_mask;
             if let Some(titlebar) = titlebar.as_ref() {
-                style_mask = NSWindowStyleMask::NSClosableWindowMask
-                    | NSWindowStyleMask::NSMiniaturizableWindowMask
-                    | NSWindowStyleMask::NSResizableWindowMask
-                    | NSWindowStyleMask::NSTitledWindowMask;
+                style_mask =
+                    NSWindowStyleMask::NSClosableWindowMask | NSWindowStyleMask::NSTitledWindowMask;
+
+                if is_resizable {
+                    style_mask |= NSWindowStyleMask::NSResizableWindowMask;
+                }
+
+                if is_minimizable {
+                    style_mask |= NSWindowStyleMask::NSMiniaturizableWindowMask;
+                }
 
                 if titlebar.appears_transparent {
                     style_mask |= NSWindowStyleMask::NSFullSizeContentViewWindowMask;

crates/gpui/src/platform/windows/window.rs

@@ -382,10 +382,17 @@ impl WindowsWindow {
         let (mut dwexstyle, dwstyle) = if params.kind == WindowKind::PopUp {
             (WS_EX_TOOLWINDOW, WINDOW_STYLE(0x0))
         } else {
-            (
-                WS_EX_APPWINDOW,
-                WS_THICKFRAME | WS_SYSMENU | WS_MAXIMIZEBOX | WS_MINIMIZEBOX,
-            )
+            let mut dwstyle = WS_SYSMENU;
+
+            if params.is_resizable {
+                dwstyle |= WS_THICKFRAME | WS_MAXIMIZEBOX;
+            }
+
+            if params.is_minimizable {
+                dwstyle |= WS_MINIMIZEBOX;
+            }
+
+            (WS_EX_APPWINDOW, dwstyle)
         };
         if !disable_direct_composition {
             dwexstyle |= WS_EX_NOREDIRECTIONBITMAP;