feat(wire): attribute updates carry source_execution_id/trace; PullTraceEvents RPC + site read-by-execution-ids

Flow Debugger (design 2026-09-05 §5.3/§5.4): AttributeValueUpdate fields 7/8 stamped by
StreamRelayActor and parsed by SiteStreamGrpcClient (older frames => null/false). New
PullTraceEvents unary RPC on SiteStreamService (same PSK-gated prefix as PullAuditEvents):
a point read of the site audit SQLite by ExecutionId OR ParentExecutionId
(ISiteAuditQueue.ReadByExecutionIdsAsync, json_extract on the codec's camelCase keys, new
IX_audit_event_occurred index, 64-id / 2000-row caps) that moves no cursor and flips no
ForwardState. Central IPullTraceEventsClient/GrpcPullTraceEventsClient mirror the audit pull
client (endpoint resolution, NodeB failover, fault => empty) and register beside it.

Claude-Session: https://claude.ai/code/session_01GSLkkHKz9JrAtmJjmQK3cP

src/ZB.MOM.WW.ScadaBridge.Commons/Interfaces/Services/ISiteAuditQueue.cs

@@ -223,4 +223,14 @@ public interface ISiteAuditQueue
     /// <param name="ct">Cancellation token.</param>
     /// <returns>A task that resolves to the number of canonical rows deleted.</returns>
     Task<int> PurgeExpiredAsync(DateTime olderThanUtc, CancellationToken ct = default);
+
+    /// <summary>
+    /// Flow Debugger (design 2026-09-05 §5.4): point read of the rows whose
+    /// <c>ExecutionId</c> OR <c>ParentExecutionId</c> is one of <paramref name="executionIds"/>
+    /// and whose <c>OccurredAtUtc</c> is at or after <paramref name="sinceUtc"/>, ordered
+    /// <c>(OccurredAtUtc, EventId)</c>, at most <paramref name="limit"/> rows. Independent of
+    /// forwarding state — moves no cursor and flips nothing. At most 64 ids per call.
+    /// </summary>
+    Task<IReadOnlyList<AuditEvent>> ReadByExecutionIdsAsync(
+        IReadOnlyCollection<Guid> executionIds, DateTime sinceUtc, int limit, CancellationToken ct = default);
 }