Keep-alive workspace panes (#89788) stay mounted while hidden, so returning
to an already-open room never remounted GroupChatWorkspace and the
mount-time bottom anchor didn't rerun — reopening group A after visiting
group B left A at the old scroll position. GroupChatMainView now subscribes
to the pane's visibility via feature-detected host.paneVisibility (always-
visible atom fallback for older SDKs) and the workspace scrolls the bottom
sentinel into view on the hidden→visible edge. Repro and fix direction from
the live-audit review comment on #90526.
Also updates the composer shape test to slice only GroupMentionInput
(GroupClarifyCard, merged since the branch was cut, legitimately uses
Input) and teaches the legacy-SDK react proxy about useMemo.
Teknium
e30388e409