feat(wire): route_to_call trace flag + child_execution_id + trace_events; route_to_set_attributes trace (additive proto + mapper)

Flow Debugger (design 2026-09-05 §5.2/§5.4): site_command.proto gains trace=7 on
RouteToCallRequestDto, child_execution_id=6 + repeated sitestream.AuditEventDto trace_events=7
on RouteToCallResponseDto, trace=6 on RouteToSetAttributesRequestDto (imports
Protos/sitestream.proto the way central_control.proto does). Mapper round-trips them; an
empty trace_events list maps to null so an untraced/older site reads as 'not traced'.
Vendored C# regenerated via docker/regen-proto.sh (csproj untouched); golden samples extended.

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

src/ZB.MOM.WW.ScadaBridge.Communication/Grpc/SiteCommandDtoMapper.cs

@@ -2420,7 +2420,8 @@ public static class SiteCommandDtoMapper
             ScriptName = request.ScriptName,
             Parameters = LooseValueCodec.ToProtoMapOrNull(request.Parameters),
             Timestamp = Ts(request.Timestamp),
-            ParentExecutionId = GuidToWire(request.ParentExecutionId)
+            ParentExecutionId = GuidToWire(request.ParentExecutionId),
+            Trace = request.Trace
         };
     }
 
@@ -2437,7 +2438,8 @@ public static class SiteCommandDtoMapper
             dto.ScriptName,
             LooseValueCodec.FromProtoMapOrNull(dto.Parameters),
             Dto(dto.Timestamp),
-            GuidFromWire(dto.ParentExecutionId));
+            GuidFromWire(dto.ParentExecutionId),
+            dto.Trace);
     }
 
     /// <summary>Projects a <see cref="RouteToGetAttributesRequest"/> onto the wire.</summary>
@@ -2485,7 +2487,8 @@ public static class SiteCommandDtoMapper
             CorrelationId = request.CorrelationId,
             InstanceUniqueName = request.InstanceUniqueName,
             Timestamp = Ts(request.Timestamp),
-            ParentExecutionId = GuidToWire(request.ParentExecutionId)
+            ParentExecutionId = GuidToWire(request.ParentExecutionId),
+            Trace = request.Trace
         };
 
         foreach (var (key, value) in request.AttributeValues)
@@ -2508,7 +2511,8 @@ public static class SiteCommandDtoMapper
             dto.InstanceUniqueName,
             dto.AttributeValues.ToDictionary(kv => kv.Key, kv => kv.Value),
             Dto(dto.Timestamp),
-            GuidFromWire(dto.ParentExecutionId));
+            GuidFromWire(dto.ParentExecutionId),
+            dto.Trace);
     }
 
     /// <summary>Projects a <see cref="RouteToWaitForAttributeRequest"/> onto the wire.</summary>
@@ -2564,14 +2568,24 @@ public static class SiteCommandDtoMapper
     {
         ArgumentNullException.ThrowIfNull(response);
 
-        return new RouteToCallResponseDto
+        var dto = new RouteToCallResponseDto
         {
             CorrelationId = response.CorrelationId,
             Success = response.Success,
             ReturnValue = LooseValueCodec.ToProtoOrNull(response.ReturnValue),
             ErrorMessage = OrEmpty(response.ErrorMessage),
-            Timestamp = Ts(response.Timestamp)
+            Timestamp = Ts(response.Timestamp),
+            // Flow Debugger (design 2026-09-05 §5.4): additive fields 6/7.
+            ChildExecutionId = GuidToWire(response.ChildExecutionId)
         };
+        if (response.TraceEvents is { Count: > 0 } traceEvents)
+        {
+            foreach (var evt in traceEvents)
+            {
+                dto.TraceEvents.Add(AuditEventDtoMapper.ToDto(evt));
+            }
+        }
+        return dto;
     }
 
     /// <summary>Rehydrates a <see cref="RouteToCallResponse"/> from the wire.</summary>
@@ -2586,7 +2600,11 @@ public static class SiteCommandDtoMapper
             dto.Success,
             LooseValueCodec.FromProto(dto.ReturnValue),
             NullIfEmpty(dto.ErrorMessage),
-            Dto(dto.Timestamp));
+            Dto(dto.Timestamp),
+            GuidFromWire(dto.ChildExecutionId),
+            // An untraced run — or an older site that never sets the field — sends no
+            // events, which maps to null so the UI can label the lane "site not traced".
+            dto.TraceEvents.Count == 0 ? null : dto.TraceEvents.Select(AuditEventDtoMapper.FromDto).ToList());
     }
 
     /// <summary>Projects a <see cref="RouteToGetAttributesResponse"/> onto the wire.</summary>

src/ZB.MOM.WW.ScadaBridge.Communication/Protos/site_command.proto

@@ -5,6 +5,9 @@ package scadabridge.sitecommand.v1;
 import "google/protobuf/timestamp.proto";
 import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";
+// Flow Debugger (design 2026-09-05 §5.4): RouteToCallResponseDto carries the site's
+// ScriptTrace rows inline as the AuditEventDto sitestream.proto already defines.
+import "Protos/sitestream.proto";
 
 // ─────────────────────────────────────────────────────────────────────────────
 // Site command plane (central → site) — the gRPC replacement for the per-site
@@ -765,6 +768,9 @@ message RouteToCallRequestDto {
   LooseValueMap parameters = 4;   // absent => null (distinct from empty)
   google.protobuf.Timestamp timestamp = 5;
   string parent_execution_id = 6; // empty string represents null
+  // Flow Debugger trace flag (design 2026-09-05 §5.2). proto3 default false = untraced,
+  // which is what an older central sends and what an older site reads.
+  bool trace = 7;
 }
 
 message RouteToCallResponseDto {
@@ -773,6 +779,12 @@ message RouteToCallResponseDto {
   LooseValue return_value = 3;   // absent => null
   string error_message = 4;      // empty string represents null
   google.protobuf.Timestamp timestamp = 5;
+  // Flow Debugger (design §5.4): the routed site run's ExecutionId ("D" GUID form;
+  // empty represents null — an older site never sets it).
+  string child_execution_id = 6;
+  // Flow Debugger (design §5.4): the site's ScriptTrace audit events for a traced run,
+  // in emission order. Empty from an untraced run or an older site (mapper => null).
+  repeated sitestream.AuditEventDto trace_events = 7;
 }
 
 message RouteToGetAttributesRequestDto {
@@ -797,6 +809,8 @@ message RouteToSetAttributesRequestDto {
   map<string, string> attribute_values = 3;
   google.protobuf.Timestamp timestamp = 4;
   string parent_execution_id = 5;   // empty string represents null
+  // Flow Debugger trace flag (design 2026-09-05 §5.2/§5.3): arms the echo stamp.
+  bool trace = 6;
 }
 
 message RouteToSetAttributesResponseDto {