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Scrum iter 9 flagged that gateway's audit row stores null for `latency_ms` — required for PRD audit-log parity. The field didn't exist; adding it now with a single Instant captured at handler entry, populated on both response paths (empty batches + non-empty result). No behavior change for existing clients — they read the JSON and ignore unknown fields. Audit-log consumers can now surface p50/p99 latency from the response body instead of inferring from tracing. Narrow fingerprint on crates/queryd already has this as a known BoundaryViolation pattern (`latency_ms-row_count` key) — iter 10 on any queryd file will see the preamble say "this was fixed in iter 10" when it runs. Workspace warnings unchanged at 11. 7 policy tests still pass. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>