Optional time range hint to bound the trace metadata lookup. When provided, the backend
restricts the AggregatedTraceMetadata query to this window (with a small buffer) and
will not fall back to a full-table scan. When absent, the backend uses a default short
window with a full-scan fallback for backward compatibility — this fallback can be
expensive on large datasets. API consumers are strongly encouraged to provide a
timeRange covering when the trace occurred.