rebase updated the state only, so the mirror the callbacks read still held the removed
row and an undo right after it wrote that row back for a moment.
Leaving the Playlists page and coming back painted the selected list empty ("0 videos") while
the rail counted its rows. The page re-seeds its undoable order from the cached list in an
effect; StrictMode runs that effect twice on the remount, so a reset was followed in the same
tick by a rebase. Since E32 S3 a reset is state only and the rebase read the mirror ref, which
still held the empty initial history, and wrote it back over the reset.
rebase is now a state updater, so it builds on whatever an earlier call in the tick installed.
Both tests seen RED (hook: [] for [10, 20]; page: no rows), and the bug reproduced in the
browser on the old hook.
peter