tests fixes

src/__Libraries/StellaOps.HybridLogicalClock/HlcTimestampJsonConverter.cs

@@ -23,7 +23,7 @@ public sealed class HlcTimestampJsonConverter : JsonConverter<HlcTimestamp>
     {
         if (reader.TokenType == JsonTokenType.Null)
         {
-            throw new JsonException("Cannot convert null value to HlcTimestamp");
+            return default;
         }
 
         if (reader.TokenType != JsonTokenType.String)

src/__Libraries/StellaOps.HybridLogicalClock/HybridLogicalClock.cs

@@ -106,8 +106,9 @@ public sealed class HybridLogicalClock : IHybridLogicalClock
         _logger = logger;
         _maxClockSkew = maxClockSkew ?? TimeSpan.FromMinutes(1);
 
-        // Initialize to current physical time
-        _lastPhysicalTime = _timeProvider.GetUtcNow().ToUnixTimeMilliseconds();
+        // Initialize to 0 so first Tick() will advance physical time and reset counter
+        // This follows the standard HLC algorithm where l starts at 0
+        _lastPhysicalTime = 0;
         _logicalCounter = 0;
 
         _logger.LogInformation(