Same-epoch reconciliation now trusts reported roles first:
- one claims primary, other replica → trust roles
- both claim primary → WALHeadLSN heuristic tiebreak
- both claim replica → keep existing, log ambiguity
Replaced addServerAsReplica with upsertServerAsReplica: checks
for existing replica entry by server name before appending.
Prevents duplicate ReplicaInfo rows during restart/replay windows.
2 new tests: role-trusted same-epoch, duplicate replica prevention.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>