FSR hudless UI mode implementation

[weicsun]

• The hudless input is pasted into a full-size internal texture s_state.m_hudlessTexture (the compute "hudless copy pass", cb.mode = 2) using the view imagePosition, imageSize, imageClipMin/Max so it matches what is shown in the view window.
• Because the frame generation path uses the callback dispatch, the swapchain backbuffer / presentColor will be whatever the app actually draws to the screen; frame generation receives the explicit HUDLessColor texture we provide (so generation uses the hudless image, while the on-screen backbuffer remains the application's rendered output).