The initial-load skeleton was rendered as an early return that replaced
the JSX containing `containerRef` / `contentRef`. On slow loads, the
200ms threshold flipped the skeleton on before messages arrived, so when
messages did arrive every scroll-affecting effect (Effect A, the
ResizeObserver, the load handler, scrollend) re-fired exactly once
against null refs and bailed — and never re-attached because no dep
changed when the skeleton finally cleared. Net: chat opened scrolled to
the top instead of the bottom; saved-anchor restore was equally broken.
Render the skeleton as an absolutely-positioned overlay alongside the
(always-mounted) scroll container so all refs stay live across the
loading transition. Encode the constraint in the spec as the
"ContainerRef invariant" so future loading/empty/error UI doesn't
reintroduce the early-return pattern.
Jannis Braun
c05c04181d