New only fell back to the legacy DefaultUnit setting when the whole
defaults file was missing or invalid, so a readable file without a
usable unit produced inches. BOM import never assigned units at all,
and the Nest Defaults dialog showed inches for a missing file.
All three now load through MainForm.LoadSavedNestDefaults, which passes
DefaultUnit as the per-field unit fallback. BOM-created nests start from
NestDefaults.ApplyTo, like New, before applying each group's plate size
and spacing.
The ApplyTo test now asserts units; removing the unit assignment from
ApplyTo fails it. WinForms behaviour is compile-verified only on Linux.
aj
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