Fix enrichment re-arm and migration backfill gaps

Three crash- and migration-recovery gaps in the unified enrichment
model left rows stuck or misclassified:

- Upsert re-armed a blank, newly-linked tracker pattern without
  clearing its prior enrichment payload. A crash between the worker's
  claim and persist then left the row with a stale payload, so the
  stale-recovery sweep (which only catches rows with a null payload)
  skipped it forever. Clear enrichment on re-arm so the row reads as
  not-yet-completed again, and pin the behavior with a test.

- The migration added last_enrichment_attempt_at to
  common_third_parties without seeding it. Rows with prior attempts
  kept a NULL clock and could never satisfy the stale-reset predicate.
  Backfill from updated_at, the historical claim-time proxy.

- The migration switched the tracker-pattern enriched-state source to
  the enrichment payload without backfilling rows previously marked by
  enriched_at, making already-enriched rows read as unenriched.
  Seed a provenance sentinel for rows that carried the old done-flag.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/coredata/migrations/20260615T161615Z.sql

@@ -30,8 +30,30 @@ ALTER TABLE common_tracker_patterns
 ALTER TABLE common_tracker_patterns
     RENAME COLUMN enriched_at TO last_enrichment_attempt_at;
 
+-- Backfill the enriched-state marker for rows that were terminally enriched
+-- under the old model. "Enriched" previously meant enriched_at IS NOT NULL (a
+-- terminal done-flag); it now means a non-null enrichment payload. The rename
+-- above moved the old done-flag into last_enrichment_attempt_at, so seed a
+-- provenance payload for every row that carried it. Without this, rows already
+-- enriched before the deploy would read as permanently unenriched. The payload
+-- carries no per-field provenance, so completeness checks treat it as fully
+-- enriched.
+UPDATE common_tracker_patterns
+SET enrichment = '{"status": "migrated"}'::jsonb
+WHERE last_enrichment_attempt_at IS NOT NULL;
+
 -- common_third_parties already carries enrichment/enrichment_attempts; give
 -- it the same explicit last-attempt timestamp (previously only recorded in
 -- the enrichment JSON) so the stale-recovery clock has a dedicated column.
 ALTER TABLE common_third_parties
     ADD COLUMN last_enrichment_attempt_at TIMESTAMP WITH TIME ZONE;
+
+-- Seed the new clock for rows that already spent an attempt. The claim path
+-- stamps last_enrichment_attempt_at and updated_at together, so updated_at is
+-- the historical proxy for the last attempt. Without this, a row claimed but
+-- never completed before the migration keeps a NULL clock, and the stale-reset
+-- predicate (last_enrichment_attempt_at < stale_before) can never be true for
+-- NULL, so it would never be re-queued. Never-attempted rows keep a NULL clock.
+UPDATE common_third_parties
+SET last_enrichment_attempt_at = updated_at
+WHERE enrichment_attempts > 0;