The matrix derives each row's label from the event name, so a new event
type gets a row whether or not anybody wrote the strings for it. That is
how SECURITY_ALERT has been rendering its own raw key since v1.23: the
forward i18n coverage test only sees literal call sites, and this key is
assembled from a runtime value.
Move the derivation out of the page so a test can compute the keys the
page computes, assert both resolve in all six bundles, and name the
missing one. Write the sign-in row's strings, and the strings for the
delegated-dose row and its push body.
