fix(oci): add response_type to embed response for SDK discriminated union

The SDK's EmbedResponse is a discriminated union on response_type
(embeddings_floats vs embeddings_by_type). The OCI embed response
transformation was missing this field, causing pydantic to return None
instead of an EmbedResponse object. This broke V1 embed when the SDK's
merge_embed_responses tried to access .meta on None.

V1 (flat float arrays) now returns response_type="embeddings_floats",
V2 (typed dict) returns response_type="embeddings_by_type".

Author: fede-kamel

src/cohere/oci_client.py

@@ -878,7 +878,10 @@ def transform_oci_response_to_cohere(
         if "billed_units" in usage:
             meta["billed_units"] = usage["billed_units"]
 
+        response_type = "embeddings_by_type" if is_v2 else "embeddings_floats"
+
         return {
+            "response_type": response_type,
             "id": oci_response.get("id", str(uuid.uuid4())),
             "embeddings": embeddings,
             "texts": [],