The settings chooser and the reminder filter treat only the capability's
primary account as the user's own, while the engine also counted any
account the server marks as personal. On a server that lists a second
such account, its address books and calendars synced although the
chooser showed them off. The engine now uses the same rule as the app.
The sync adapters from ed2525e start a headless task for every sync, but
the task only reported "disabled". This adds the engine it runs
(`src/device-sync/engine`, `src/device-sync/jmap`): for one Android
account and authority it downloads the server's changes, uploads what
the device changed, and hands a report back to SyncManager.
- Downloads follow `/changes` from the state kept in the provider's
SyncState. Rows and the state they reach are written in one batch, so
a killed run resumes where it stopped. Without a state, after
`cannotCalculateChanges` or after the user discarded deletions, a full
reconcile compares ids instead.
- Uploads go in three phases across accounts (creates, updates,
deletions), so moving an item to another account never destroys it
before the copy exists. A create carries a uid written to the device
first, and the server is asked for that uid before creating, so a lost
response or a killed run never makes a duplicate. Updates are patches
guarded by `ifInState`; nothing is replaced whole.
- More than 50 deletions that are also more than a fifth of the synced
items hold every deletion back and report `tooManyDeletions`, so
Android asks the user; "undo" restores the items from the server.
- An item the server refuses is marked and not sent again until it
changes or its back-off (1 hour, doubling to a day) ends. Such
refusals and planner errors stay with their item; the rest of the run
goes on.
- Runs of one account and authority take a lock, stop at checkpoints
when cancelled or close to the deadline, and never throw: every
failure becomes an outcome, and a rejected sign-in posts one "Sign in
again" notification.
- The JMAP side uses a client of its own per app account, never the
UI's, since a run can share the JS runtime with the app.
Turning sync off or signing out runs the same upload first
(`teardownAuthority`) and deletes the rows only once nothing is waiting,
or when the user agreed to lose it.
The planners that map items to rows land in the next commits; until
then a run fails before it touches a row.
Checked: 94 engine tests against the fake provider and JMAP server
(sync flows, failures, crashes and retries, teardown), and `npm run
typecheck`, `npm test` and `npm run i18n:check` on this commit.