Applies rule 32's migration exception: each header still says what the
schema was, what changes and what it prevents, but task, milestone,
decision and rule ids are replaced by the practice they stood for, the
operator quotes by the decision, single-install counts are dropped, and
pointers to a deleted package and an external design doc are gone.
golang-migrate keeps no checksum, so editing applied migrations'
comments is safe.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Table was referenced in migration 0005's comment but never created —
this slice fills the gap. Soft-delete via deleted_at column; hot-path
partial index on active rows; GIN index on session_vector for
M3 sub-plan #3's similarity queries.