`web_surface.rs` had crept to 548 lines; six unrelated input-recorder
methods (scroll delta, viewport size, native surface, hover point,
click point, typed text) dominated the file. Move them into a sibling
`web_surface_input.rs` so the store file (now 338 lines) is the
ensure / tick / lifecycle facade and the input file is a flat set of
`record_*` methods on the same struct.
`surfaces`, `keyboard_focus`, and `surface_mut` become `pub(super)` so
the sibling can reach them; everything else stays private.
ZacharyZhang-NY
dabb965afd