Wayland: fixed-size tiled window reverts to stale floating size

Howdy, found a Wayland size-cache edge case: - A borderless, modal, non-resizable window is created at 1×1, then resized to 592×185. - When configured as tiled, `windowed`, `requested`, and `pending` are all 592×185, but `floating` remains 1×1. - The fixed-size configure branch then copies `window->floating` over the correct requested size, reverting the surface to 1×1. - Reproduced with SDL 3.4.4 on Hyprland through Unreal Engine 5.8.1. The relevant code is unchanged in 3.4.8 and `main`; XWayland works correctly. The fixed-size branch should preserve `wind->requested` instead of replacing it with the stale floating size. Related: [#4598](https://github.com/libsdl-org/SDL/pull/4598), [#7443](https://github.com/libsdl-org/SDL/pull/7443), [#10320](https://github.com/libsdl-org/SDL/pull/10320). Happy to test a patch or put together a standalone reproducer if useful.