The page being shown.
The host's translator — the labels resolve at render, so a language switch while the dialog is open re-localizes them.
A helper rather than an action-model protocol: a second host (a taskpane, the script editor) reuses
ten lines of button logic by calling this, instead of implementing an interface to be handed the
same array. OptionsDialog re-reads options/defaultOption every render, so a page flip needs
nothing else.
The action row for a page — FIRST entry is the default (
OptionsDialog's own rule).