Main replaced the chat timeline scroll engine while this branch was in
flight, which obsoletes two of its subareas and reshapes a third:
- Chat timeline: main's LegendList-based MessageList/ChatContainer win;
the activation-overscan staircase targeted the removed tanstack path
(LegendList provides adaptive rendering natively) and is dropped along
with its test.
- Scroll shadows: main's hook-based masks stay (the virtualized list owns
its scroll element — there is no wrapper to hand the styling to); the
viewport-wrapper ScrollShadow rewrite, its index.css replacement, its
test, and the call-site viewportClassName adaptations are reverted to
main. The chat OverlayScrollbar keeps this branch's disableHorizontal.
- OverlayScrollbar: the direct-DOM rewrite lands, but binding now follows
the live container node instead of binding once per ref object — the
chat scroller remounts on every session switch, and a bind-once
contract left the scrollbar attached to a dead element.
- Markdown renderer: the detached-DOM cache and warm-block fast path
merge with main's block-commit reveal (enter cascade), streaming code
highlighting, and gutter reservation; the per-block reconcile keeps
both the decoration-refresh path and the reveal cascade.
Bohdan Triapitsyn
ac880e8e62