feat(commons): additive Trace flag + ChildExecutionId/TraceEvents on route/call/write/change records

Flow Debugger (design 2026-09-05 §5.2/§5.4): Trace rides beside ParentExecutionId on
RouteToCallRequest/RouteToSetAttributesRequest/ScriptCallRequest/SetStaticAttributeCommand/
AttributeValueChanged; RouteToCallResponse and ScriptCallResult carry the site run's
ExecutionId and its ScriptTrace AuditEvents inline. All trailing optional — zero call-site edits.

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

src/ZB.MOM.WW.ScadaBridge.Commons/Messages/InboundApi/RouteToInstanceRequest.cs

@@ -1,3 +1,5 @@
+using ZB.MOM.WW.Audit;
+
 namespace ZB.MOM.WW.ScadaBridge.Commons.Messages.InboundApi;
 
 /// <summary>
@@ -12,23 +14,29 @@ namespace ZB.MOM.WW.ScadaBridge.Commons.Messages.InboundApi;
 /// Additive trailing member — null for requests built before the field existed
 /// or for routed calls with no spawning execution (e.g. the Central UI sandbox).
 /// </param>
+/// <param name="Trace">Flow Debugger trace flag — see design 2026-09-05 §5.2. Additive; defaults to untraced.</param>
 public record RouteToCallRequest(
     string CorrelationId,
     string InstanceUniqueName,
     string ScriptName,
     IReadOnlyDictionary<string, object?>? Parameters,
     DateTimeOffset Timestamp,
-    Guid? ParentExecutionId = null);
+    Guid? ParentExecutionId = null,
+    bool Trace = false);
 
 /// <summary>
 /// Response from a Route.To() call.
 /// </summary>
+/// <param name="ChildExecutionId">Flow Debugger — the routed site run's <c>ExecutionId</c> (design 2026-09-05 §5.4); null from a site that predates the field.</param>
+/// <param name="TraceEvents">Flow Debugger — the site's <c>ScriptTrace</c> audit events for a traced run, in emission order (design 2026-09-05 §5.4); null when untraced or from an older site.</param>
 public record RouteToCallResponse(
     string CorrelationId,
     bool Success,
     object? ReturnValue,
     string? ErrorMessage,
-    DateTimeOffset Timestamp);
+    DateTimeOffset Timestamp,
+    Guid? ChildExecutionId = null,
+    IReadOnlyList<AuditEvent>? TraceEvents = null);
 
 /// <summary>
 /// Request to read attribute(s) from a remote instance.
@@ -68,12 +76,14 @@ public record RouteToGetAttributesResponse(
 /// write path. Additive trailing member — null for the Central UI sandbox path or for
 /// callers built before the field existed.
 /// </param>
+/// <param name="Trace">Flow Debugger trace flag — see design 2026-09-05 §5.2. Additive; defaults to untraced.</param>
 public record RouteToSetAttributesRequest(
     string CorrelationId,
     string InstanceUniqueName,
     IReadOnlyDictionary<string, string> AttributeValues,
     DateTimeOffset Timestamp,
-    Guid? ParentExecutionId = null);
+    Guid? ParentExecutionId = null,
+    bool Trace = false);
 
 /// <summary>
 /// Response confirming attribute writes on a remote instance.