ConstNo Apply button, for the same reason the Sheet tab has none: every control is one unambiguous act,
and a pane is not a dialog. Encryption still only reaches the FILE on the next save — but that is
about when bytes are written, not about when the intent is recorded, and origin.setPassword has
always recorded it the moment it is given. An Apply button in front of that only added a step.
The two halves commit through different objects: structure is a model change
(IWorkbookProtection, effective at once), encryption is a property of the io handle. See
PROTECTION-DESIGN.md §5g.
The Workbook tab of Manage Protection — WorkbookProtectionPanel bound to the model.