ltk: convert physical sizes to logical for overlays and input regions on HiDPI

Overlay `set_size` and input regions were handed physical (layout-space) pixels straight to layer-shell and `wl_region`, both of which expect logical coordinates. They only coincide at scale 1, so on a scale-2 output every overlay requested a surface twice its intended size and the input region covered the wrong area.
`apply_input_region` now takes the surface scale and divides each `Rect` down to logical before adding it to the region; the four draw paths (software and gles, full and partial) forward their scale. `reconcile_overlays` converts `OverlaySpec::size` to logical for both `set_size` and the initial `OverlayConfig` (0 = fill survives the divide), and seeds the new surface's `scale_factor` from the parent so the first configure allocates a HiDPI buffer instead of rendering at scale 1 until `scale_factor_changed` lands a frame or two later.

src/draw/chrome.rs

@@ -84,15 +84,23 @@ pub( crate ) fn apply_input_region(
 	wl_surface:   &WlSurface,
 	compositor:   &CompositorState,
 	input_region: Option<&[Rect]>,
+	scale:        u32,
 )
 {
 	if let Some( regions ) = input_region
 	{
 		if let Ok( region ) = Region::new( compositor )
 		{
+			// `Rect`s are physical (layout space); `wl_region` is logical.
+			let s = scale.max( 1 ) as f32;
 			for r in regions
 			{
-				region.add( r.x as i32, r.y as i32, r.width as i32, r.height as i32 );
+				region.add(
+					( r.x      / s ).round() as i32,
+					( r.y      / s ).round() as i32,
+					( r.width  / s ).round() as i32,
+					( r.height / s ).round() as i32,
+				);
 			}
 			wl_surface.set_input_region( Some( region.wl_region() ) );
 		}