Moving a message across the account boundary (own ↔ shared folder, or
between two owners' shared folders) left the original in the source
folder and showed the moved copy as unread. Same-account moves were fine.
Cause (verified against a live Stalwart):
- Email/copy drops keywords unless the create sets them, so the copy lost
$seen and arrived unread.
- onSuccessDestroyOriginal is unreliable — the implicit destroy reports
notFound and leaves the original behind (flaky), so the move duplicated.
Fix (copyEmailAcrossAccounts): read the source keywords and carry them
into the Email/copy create, then destroy the original with an explicit
Email/set on the source account instead of onSuccessDestroyOriginal.
Tests: 08-shared-moves now asserts the source is gone and the read state
survives on every cross-account case, and adds a cross-owner shared →
shared move (alice's folder → bob's folder). Confirmed red on the old
code (3 cross-account cases fail), green with the fix.
Stefan Hildebrandt
6248bb9825