#331: use default codec (Avro) instead of hardcoded json in PayloadEnvelopeResolver and CodecRegistry

PayloadEnvelopeResolver::resolve() now uses CodecRegistry::defaultCodec()
instead of hardcoding json when wrapping plain array input.

CodecRegistry::universal() now returns [avro] only — json is no longer
a universal v2 codec (per #334, Avro is the only v2 codec).

Author: durable-workflow-ops

src/Serializers/CodecRegistry.php

@@ -15,7 +15,7 @@
  *
  * Canonical names:
  *   - "avro"                    — Apache Avro binary codec (default for new workflows)
- *   - "json"                    — language-neutral JSON (supported, not default)
+ *   - "json"                    — language-neutral JSON (v1 migration reads only, not for new v2 workflows)
  *   - "workflow-serializer-y"   — PHP SerializableClosure with byte-escape encoding (legacy)
  *   - "workflow-serializer-base64" — PHP SerializableClosure with base64 encoding (legacy)
  *
@@ -123,7 +123,7 @@ public static function names(): array
      */
     public static function universal(): array
     {
-        return ['json', 'avro'];
+        return ['avro'];
     }
 
     /**

src/V2/Support/PayloadEnvelopeResolver.php

@@ -14,7 +14,7 @@
  * The worker protocol carries every payload as `{codec, blob}`. Clients may
  * send `input` in two shapes on the HTTP API:
  *
- *   1. A plain JSON array of arguments  →  codec "json", blob = JSON bytes
+ *   1. A plain array of arguments  →  encoded with the configured default codec (Avro)
  *   2. An explicit envelope object `{codec: "<name>", blob: "<opaque>"}`
  *      →  codec = the declared name, blob = the opaque string as-is
  *
@@ -155,8 +155,8 @@ public static function resolve($input, string $field = 'input'): array
         $values = array_values($input);
 
         return [
-            'codec' => 'json',
-            'blob' => Serializer::serializeWithCodec('json', $values),
+            'codec' => CodecRegistry::defaultCodec(),
+            'blob' => Serializer::serializeWithCodec(CodecRegistry::defaultCodec(), $values),
         ];
     }