- merger: deduplicate hits by primary key when multiple shards map to same node
- search: use shared AppState with live topology from health checker
- search: strip _miroir_shard always, _rankingScore only when not requested
- search: include facetDistribution only when facets were requested
- credentials: add mutex guards for env-var test isolation
- Add Phase 2 DoD integration tests: shard coverage, dedup, facets, paging,
degraded writes, error shape parity, topology shape, auth errors, reserved fields
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>