managed agents: surface prompt on AgentOut

Reads the existing prompt column on the agent row and includes it on
GET /agents and GET /agents/{id} responses. The agent-platform UI
needs it to show a one-line description on the root agents list.

litellm/proxy/managed_agents_endpoints/endpoints_agents.py

@@ -46,6 +46,7 @@ def _agent_row_to_out(row) -> AgentOut:
         id=row.agent_id,
         name=row.agent_name,
         model=row.model,
+        prompt=getattr(row, "prompt", None),
         template_id=row.template_id,
         branch=row.branch,
         pfp_url=pfp_url if isinstance(pfp_url, str) else None,

litellm/proxy/managed_agents_endpoints/types.py

@@ -100,6 +100,7 @@ class AgentOut(BaseModel):
     id: str
     name: Optional[str] = None
     model: str
+    prompt: Optional[str] = None
     template_id: str
     branch: str
     pfp_url: Optional[str] = None