Three uuids on one arrival, three different answers

Asked of the row the feed actually returns.

site_id had a reference all along and the feed was not sending it. A
client could read the shop's NAME off an arrival and still had no way to
ask for that shop except by uuid - the exact gap the reference scheme
exists to close. site_slug now travels with it.

visit_id stays a uuid and needs no reference: no route takes it, it is a
key a client de-duplicates on because delivery is at-least-once, and
nobody says a visit id out loud.

The uuid in a face URL must STAY random. visit_faces.id is
gen_random_uuid() and a derived or sequential one would let somebody
walk a shop's customers by date - the same reason bucket keys are random
rather than derived from the event id. A readable identifier is right
for a customer and wrong for the thing that points at their photograph.

And seq is now json:"-". visits.seq is a plain bigserial, so it counts
every visit on the PLATFORM, and shipping it put the total footfall of
every customer we have on every row of every tenant's feed - the same
German-tank estimate that decided visitors.number had to be per client.
It was a convenience for "have I fallen behind", nothing ever read it,
and the cursor answers that without disclosing a number. The SSE event
id was never the raw value; it has always been the opaque cursor.

The one test that broke was reading seq back off the wire to assert the
cursor pointed at the last row of a burst. It asserts against the seeded
position now: the property is unchanged, and the test can no longer see
what a client cannot.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HViLj9gYNRtSr7YVZmW5sn

server/internal/store/api_arrivals.go

@@ -12,7 +12,7 @@ import (
 // mean the first poll of a feed and every poll after it returned different
 // shapes, which is the kind of bug that only shows up under load.
 const arrivalColumns = `
-	vi.id::text, vi.seq, vi.occurred_at, vi.site_id::text, si.name, vi.camera_id,
+	vi.id::text, vi.seq, vi.occurred_at, vi.site_id::text, si.name, si.slug, vi.camera_id,
 	vi.is_new_visitor, vi.similarity, vi.quality, vi.attributes, vi.image_key,
 	COALESCE(vi.visitor_id::text, ''),
 	COALESCE(vs.number, 0),
@@ -113,7 +113,7 @@ func (s *Store) Arrivals(ctx context.Context, q api.ArrivalQuery) ([]api.Arrival
 		var sim, qual *float64
 		var imageKey string
 		var number int64
-		if err := rows.Scan(&a.VisitID, &a.Seq, &at, &a.SiteID, &a.Site, &a.CameraID,
+		if err := rows.Scan(&a.VisitID, &a.Seq, &at, &a.SiteID, &a.Site, &a.SiteSlug, &a.CameraID,
 			&a.IsNew, &sim, &qual, &a.Attributes, &imageKey,
 			&a.VisitorID, &number, &a.Label, &a.Name); err != nil {
 			return nil, err