WASM canvas resize: skip with_surface_size on wasm (alt to #431)

#432 in DioxusLabs/blitz — merged 2026-05-12

Alternative to #431 implementing @nicoburns's hypothesis: drop .with_surface_size(...) on wasm so winit-web never writes inline canvas.style.width/height, letting host CSS size the canvas directly — no style-stripping needed. Same wgpu surface.configure debounce as #431 (with timer coalescing to avoid closure leaks during drag), plus a fallback that seeds the initial size from the canvas's CSS layout when winit-web reports 0×0 at init.