batchUpsertSurfaceElos now writes only to the canonical
participant_surface_elos table (the mirror step is now the only step).
getSurfaceElosForSeason joins through season_participants → canonical
participants so the admin UI keeps its existing (id, participantId,
sportsSeasonId, ...) row shape.
season_participants without a canonical link get silently skipped. In
practice every qualifying-points roster entry is canonical-linked after
Phase 2 backfill + Phase 3 auto-linking on createParticipant.
Phase 4 Tasks 2 + 3 of canonical tournament layer migration.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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