Add design + 5 phase plans: canonical tournament & participant layer
Spec and phased implementation plans for eliminating data duplication
across overlapping qualifying-points windows (golf, tennis, CS2) by
introducing canonical tournaments, participants, tournament_results,
and surface-Elo tables above the existing per-window layer.
- Phase 1a: rename existing per-window tables to season_* prefix
- Phase 1b: create canonical tables + nullable FKs
- Phase 2: backfill canonical from existing in-flight windows
- Phase 3: cutover - sync service, admin UI, simulator read switch
- Phase 4: cleanup - drop deprecated tables and routes
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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