The progress store merged like the mark stores do, keeping whichever copy had
the earlier timestamp. That is right for a mark — `at` is when the reader made
it, membership is the whole fact, and the oldest stamp is the truest one — and
wrong here, because this record *is* the data. A status, an effort, a note and
whether an event repeats all live in it, and `at` says when one of those last
changed.
So the earlier copy winning discarded every edit made after it, in both of the
directions an import actually happens in: restoring a backup taken before an
evening's work undid the evening, and importing an old file onto a device with
newer progress rolled the device back. Neither is recoverable — there is no
account and no server holding a second copy.
The later record wins now. Nothing is removed in either direction, and taking
the maximum of two timestamps is as order-independent and idempotent as the rule
it replaces. `mergeProgress` came out of the hook to be tested, which is also
how the ignored store's opposite rule is now written down rather than assumed.
Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
