The notification action (`NotificationItem`) rendered as
`variant="textStrong" size="xs"` — an 11px underlined muted-grey text link
with a ~44x20px hit target. On the data-training confirm toast raised by
`surfaceModelSwitchConfirm` / `confirmModelWarning` (e.g. picking
`muse-spark-1.2-contributor`) it read as a footnote, not the one action
the toast exists for, and users reported not being able to "press to
accept".
Promote it to the SDK's `default` variant at `size="sm"`: a filled
primary button, larger hit target, obvious affordance. No new styles.
Salvaged from #96562 (toast half only). Refs #96563.
37fd6eea97