Eleven parallel BTreeMaps (click_points, hover_points,
pending_scroll_deltas, scroll_offsets, typed_texts, viewport_bounds,
viewport_sizes, pending_viewport_sizes, states, etc.) made every
input bug a coordination problem across 11 disjoint maps with no
compile-time guarantee they stayed in sync. Collapse them into
BTreeMap<TabId, PerTabSurface>: one owner per tab, one lookup per
input event. keyboard_focus stays at the store level because only
one tab in the window can hold focus at a time.
Public API and behavior are unchanged; the previously-fixed
"scroll keeps keyboard_focus" semantics are preserved. cargo test
ely_browser_core + cargo test ely_app --bin ely_app green.
ZacharyZhang-NY
dc06d5590d