perry/ui: option to start window maximized / fullscreen on launch #1280

Summary

Add an API to launch a perry/ui window in the maximized (or fullscreen) state, instead of the explicit width/height it currently requires. Requested for Windows in discussion #1232, but should work cross-platform.

Current state

The window-creation API only accepts a fixed size:

• Windows backend (crates/perry-ui-windows/src/ffi/app_window.rs): perry_ui_app_create(title, width, height) + set_size / set_min_size / set_max_size.
• macOS backend (crates/perry-ui-macos/src/lib_ffi/window_misc.rs): mirrors the same surface.

Searching the workspace for maximize, maximized, zoom, fullscreen, SW_MAXIMIZE, WS_MAXIMIZE, showMaximized, windowState returns no hits — there is no programmatic way to start maximized today. The Win32 backend already uses ShowWindow but never with SW_MAXIMIZE/SW_SHOWMAXIMIZED.

Proposed shape

TypeScript-side, something like:

const app = createApp({
  title: "My App",
  windowState: "maximized", // "normal" (default) | "maximized" | "fullscreen"
});

Behind the scenes:

• Windows: call ShowWindow(hwnd, SW_SHOWMAXIMIZED) on first show (or fullscreen via removing WS_OVERLAPPEDWINDOW and resizing to the monitor rect).
• macOS: NSWindow.zoom(_:) for maximize / toggleFullScreen(_:) for fullscreen, called from the MainThreadMarker path.
• Linux/GTK4 (if in scope): gtk_window_maximize / gtk_window_fullscreen.

Width/height should remain optional; if both are provided alongside windowState: "maximized", the maximized state wins on launch but the saved restore size honors them.

Linked discussion

• how to make perry gui start with window maximized as default in windows ? #1232 — original ask (Windows).