knip: ui-settings no longer imports react-dom (the portal moved into
OnboardingSurface), so the react-dom peer/dev dependencies and
@types/react-dom go away with the usage.
Review follow-ups: the Agent Note's Testing section now records the
held-join reload regression scenario this PR adds (both languages,
pairing re-recorded); the e2e hold gates EVERY settings.describe issued
before release instead of only the first, so a future boot-time join
consumer cannot silently collapse the widened window; the sampler's
persistence across later navigations is documented and the vacuity
wording softened to what the hold actually buys (timing independence).