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>
c47523e5bd