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.rs

@@ -1091,6 +1091,12 @@ pub struct WindowOptions {
     /// Whether the window should be movable by the user
     pub is_movable: bool,
 
+    /// Whether the window should be resizable by the user
+    pub is_resizable: bool,
+
+    /// Whether the window should be minimized by the user
+    pub is_minimizable: bool,
+
     /// The display to create the window on, if this is None,
     /// the window will be created on the main display
     pub display_id: Option<DisplayId>,
@@ -1133,6 +1139,14 @@ pub(crate) struct WindowParams {
     #[cfg_attr(any(target_os = "linux", target_os = "freebsd"), allow(dead_code))]
     pub is_movable: bool,
 
+    /// Whether the window should be resizable by the user
+    #[cfg_attr(any(target_os = "linux", target_os = "freebsd"), allow(dead_code))]
+    pub is_resizable: bool,
+
+    /// Whether the window should be minimized by the user
+    #[cfg_attr(any(target_os = "linux", target_os = "freebsd"), allow(dead_code))]
+    pub is_minimizable: bool,
+
     #[cfg_attr(
         any(target_os = "linux", target_os = "freebsd", target_os = "windows"),
         allow(dead_code)
@@ -1191,6 +1205,8 @@ impl Default for WindowOptions {
             show: true,
             kind: WindowKind::Normal,
             is_movable: true,
+            is_resizable: true,
+            is_minimizable: true,
             display_id: None,
             window_background: WindowBackgroundAppearance::default(),
             app_id: None,