[Docs] optimize and supplement docs system (#86)

Signed-off-by: Gaohan123 <gaohan19@huawei.com>

vllm_omni/engine/__init__.py

@@ -49,6 +49,19 @@ class AdditionalInformationPayload(msgspec.Struct):
 
 
 class OmniEngineCoreRequest(EngineCoreRequest):
+    """Engine core request for omni models with embeddings support.
+
+    Extends the base EngineCoreRequest with support for prompt embeddings
+    and additional information payloads, enabling direct transfer of
+    pre-computed embeddings between pipeline stages.
+
+    Attributes:
+        prompt_embeds: Optional serialized prompt embeddings payload for
+            direct transfer between stages
+        additional_information: Optional serialized additional information
+            dictionary containing tensors or lists to pass along with the request
+    """
+
     # Optional prompt embeddings (direct-transfer version)
     prompt_embeds: Optional[PromptEmbedsPayload] = None
     # Optional additional information dictionary (serialized)