Snooze, the handled-occurrence watermark and the skip watermark need somewhere
to live that survives a process death. They go in their own table rather than
as columns on alarms: a missing row is the initial record, and the FK cascade
means deleting an alarm cannot leave orphaned ring state behind.
Schema v2 is exported and committed alongside v1, so MIGRATION_1_2 is
reviewable and testable rather than taken on faith.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>