fix(a2a): scope a2a lazy-feature so it doesn't subsume /v1/a2a/discover

- _lazy_features.py: use /a2a prefix + /message/send suffix for the
  a2a feature so a request to /v1/a2a/discover no longer triggers the
  a2a_endpoints module to load alongside a2a_registration.
- agent_endpoints/endpoints.py: drop the no-op description override
  kwarg from _build_merged_agent_card and its three call sites. The
  upstream card's description is already preserved by merge_agent_card's
  deepcopy, so passing it explicitly did nothing.

litellm/proxy/_lazy_features.py

@@ -92,7 +92,10 @@ LAZY_FEATURES: Tuple[LazyFeature, ...] = (
     LazyFeature(
         name="a2a",
         module_path="litellm.proxy.agent_endpoints.a2a_endpoints",
-        path_prefixes=("/a2a", "/v1/a2a"),
+        # ``/v1/a2a/{agent_id}/message/send`` is caught via the suffix so the
+        # ``/v1/a2a`` prefix doesn't subsume the discover prefix below.
+        path_prefixes=("/a2a",),
+        path_suffixes=("/message/send",),
     ),
     LazyFeature(
         name="a2a_registration",

litellm/proxy/agent_endpoints/endpoints.py

@@ -49,7 +49,6 @@ def _build_merged_agent_card(
     agent_id: str,
     http_request: Request,
     agent_name: Optional[str] = None,
-    description: Optional[str] = None,
 ) -> Dict[str, Any]:
     """Apply the LiteLLM-fronting merge to ``upstream_card`` for ``agent_id``."""
     proxy_base = _proxy_base_url(http_request)
@@ -58,7 +57,6 @@ def _build_merged_agent_card(
         proxy_url=f"{proxy_base}/a2a/{agent_id}",
         proxy_base_url=proxy_base,
         name=agent_name,
-        description=description,
     )
 
 
@@ -390,7 +388,6 @@ async def create_agent(
                 agent_id=new_agent_id,
                 http_request=http_request,
                 agent_name=request.get("agent_name"),
-                description=upstream_card.get("description"),
             )
             agent_to_create = {**request, "agent_card_params": merged_card}  # type: ignore[typeddict-item]
 
@@ -599,7 +596,6 @@ async def update_agent(
                 agent_id=agent_id,
                 http_request=http_request,
                 agent_name=request.get("agent_name"),
-                description=upstream_card.get("description"),
             )
             agent_to_update = {**request, "agent_card_params": merged_card}  # type: ignore[typeddict-item]
 
@@ -711,7 +707,6 @@ async def patch_agent(
                 agent_id=agent_id,
                 http_request=http_request,
                 agent_name=request.get("agent_name"),
-                description=upstream_card.get("description"),
             )
             patch_payload = {**request, "agent_card_params": merged_card}  # type: ignore[typeddict-item]