consolidate() has existed since #1074 and described this exact symptom in its own
comment, but its only caller was recluster() — i.e. when an admin pressed
Re-group people. After a normal background scan the centroids converged and
nobody looked, so a gallery settled with 14 people that should have been 8.
It now runs when a scan drains. There is no scan-finished event to hook, so an
idle worker asks whether the events it touched have actually drained — 'a worker
went idle' is deliberately not treated as sufficient, because with concurrency
above one the others may still be working.
The uncertain band asks instead of acting: pairs between the assignment
threshold and the stricter auto-merge one surface as accept/dismiss suggestions,
with sticky dismissals. Nothing merges silently — a pass that merged anything
reports it and points at Split.
Review rounds hardened it against overruling explicit decisions: it no longer
absorbs ignored clusters (mergePeople ORs is_ignored onto the survivor, which
would have hidden a real person), no longer merges dismissed pairs, no longer
undoes a manual Split (which now records a separation), and no longer runs after
detection is switched off. The dismissal read fails closed, a failed pass is
retried with backoff rather than lost or hot-looped, and the new table follows
event_people out of exports and backups.
Name autocomplete needs no endpoint — the people list already open is the source,
and it is event-scoped on purpose.
Known limitation, tracked in #1132: separations are keyed on person ids, so a
full re-scan loses them.
Reported by @BraynArts.
