fix: backport engine fixes from Serdica integration

1. Handle duplicate JSON property names in ToRuntimeValue — GroupBy
   before ToDictionary prevents crash on case-insensitive duplicates
2. Normalize decimal-valued integers in sub-workflow payloads —
   recursive NormalizePayloadNumbers converts 201000256548.0 to long
3. Add WorkflowExecutionActorContext — AsyncLocal propagation of
   actor identity through OnComplete execution chains

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Workflow/__Libraries/StellaOps.Workflow.Abstractions/WorkflowCanonicalExpressionRuntime.cs

@@ -480,10 +480,12 @@ public static class WorkflowCanonicalExpressionRuntime
             JsonValueKind.Number when element.TryGetInt64(out var int64Value) => int64Value,
             JsonValueKind.Number when element.TryGetDecimal(out var decimalValue) => decimalValue,
             JsonValueKind.Number when element.TryGetDouble(out var doubleValue) => doubleValue,
-            JsonValueKind.Object => element.EnumerateObject().ToDictionary(
-                x => x.Name,
-                x => ToRuntimeValue(x.Value),
-                StringComparer.OrdinalIgnoreCase),
+            JsonValueKind.Object => element.EnumerateObject()
+                .GroupBy(x => x.Name, StringComparer.OrdinalIgnoreCase)
+                .ToDictionary(
+                    g => g.Key,
+                    g => ToRuntimeValue(g.Last().Value),
+                    StringComparer.OrdinalIgnoreCase),
             JsonValueKind.Array => element.EnumerateArray().Select(ToRuntimeValue).ToArray(),
             _ => element.ToString(),
         };

src/Workflow/__Libraries/StellaOps.Workflow.Abstractions/WorkflowExecutionActorContext.cs

@@ -0,0 +1,35 @@
+using System.Threading;
+
+namespace StellaOps.Workflow.Abstractions;
+
+/// <summary>
+/// Propagates the authenticated actor ID through async workflow execution chains
+/// (e.g., OnComplete -> Call -> transport) where the original request context
+/// is not available. Implementations set ActorId and CallerUserId during
+/// task-complete/start-workflow processing.
+/// </summary>
+public sealed class WorkflowExecutionActorContext
+{
+    private static readonly AsyncLocal<string?> CurrentActorId = new();
+    private static readonly AsyncLocal<string?> CurrentCallerUserId = new();
+
+    /// <summary>
+    /// The actor ID from the task operation request (e.g., numeric user account ID).
+    /// Used for role resolution and task assignment.
+    /// </summary>
+    public string? ActorId
+    {
+        get => CurrentActorId.Value;
+        set => CurrentActorId.Value = value;
+    }
+
+    /// <summary>
+    /// The authenticated caller's user ID extracted from the HTTP request context.
+    /// Used by transport implementations for backend service calls.
+    /// </summary>
+    public string? CallerUserId
+    {
+        get => CurrentCallerUserId.Value;
+        set => CurrentCallerUserId.Value = value;
+    }
+}

src/Workflow/__Libraries/StellaOps.Workflow.Abstractions/WorkflowRegistrationAbstractions.cs

@@ -78,6 +78,7 @@ public static class WorkflowRegistrationServiceCollectionExtensions
     private static readonly JsonSerializerOptions SerializerOptions = new(JsonSerializerDefaults.Web)
     {
         PropertyNameCaseInsensitive = true,
+        NumberHandling = global::System.Text.Json.Serialization.JsonNumberHandling.AllowReadingFromString,
     };
 
     public static IServiceCollection AddWorkflowRegistration<TWorkflow>(
@@ -190,7 +191,8 @@ public static class WorkflowRegistrationServiceCollectionExtensions
             return new Dictionary<string, object?>(payload, StringComparer.OrdinalIgnoreCase);
         }
 
-        var json = JsonSerializer.Serialize(payload, SerializerOptions);
+        var normalized = NormalizePayloadNumbers(payload);
+        var json = JsonSerializer.Serialize(normalized, SerializerOptions);
         return JsonSerializer.Deserialize(json, startRequestType, SerializerOptions)
             ?? throw new InvalidOperationException(
                 $"Unable to bind workflow payload to '{startRequestType.FullName}'.");
@@ -291,5 +293,27 @@ public static class WorkflowRegistrationServiceCollectionExtensions
         };
     }
 
+    private static IDictionary<string, object?> NormalizePayloadNumbers(IDictionary<string, object?> payload)
+    {
+        var result = new Dictionary<string, object?>(payload.Count, StringComparer.OrdinalIgnoreCase);
+        foreach (var kvp in payload)
+        {
+            result[kvp.Key] = NormalizeValue(kvp.Value);
+        }
+        return result;
+    }
+
+    private static object? NormalizeValue(object? value)
+    {
+        return value switch
+        {
+            decimal d when d == Math.Truncate(d) && d >= long.MinValue && d <= long.MaxValue => (long)d,
+            double d when d == Math.Truncate(d) && d >= long.MinValue && d <= long.MaxValue => (long)d,
+            IDictionary<string, object?> dict => NormalizePayloadNumbers(dict),
+            object[] arr => arr.Select(NormalizeValue).ToArray(),
+            _ => value,
+        };
+    }
+
     private sealed record WorkflowBusinessReferencePartProperty(PropertyInfo Property, string PartName);
 }