Form requires title + primary_attachment; the primary-row picker is
compact in edit mode (dashed-border when empty, filename row when
filled). Detail view promotes the primary to a gold signature block
(48×60 thumb + filename + meta + ↓ download · 🔍 preview). For image-
mime primaries, the thumb lazy-loads via decrypt + object-URL; the
preview button toggles an inline expanded view.
Supplementary attachments use the standard compact disclosure (Task 7)
when present.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
705b171553