lastReconciled

The channel set the stored conversations are currently keyed against, encoded as a ChannelSet.

Conversations are keyed by channel index, so they have to be re-keyed whenever a slot changes occupant. This is the baseline that change is measured from. It is persisted rather than held in memory because the radio reboots after a preset change and the app is routinely killed across that gap; an in-memory baseline would be lost exactly when it is needed, leaving the messages permanently misfiled. Null before the first reconcile — then the current set is captured and nothing moves.

Survives ChannelSetDao.clearRetainingBaseline, which the handshake uses: the messages have not moved just because the cached channel set was dropped.