Fix SwarmConfigLoader to handle agent top-level key requirement

- Wrap individual agent configs in 'agent:' key when loading swarm agents
- Fixes compatibility with AgentConfigLoader top-level key requirement
- Resolves swarm loading errors in configuration-driven systems

Fixes issue where swarm agents failed to load with:
'Configuration must contain a top-level agent key'

Author: vawsgit

src/strands/experimental/config_loader/swarm/swarm_config_loader.py

@@ -228,7 +228,9 @@ def load_agents(self, agents_config: List[Dict[str, Any]]) -> List[Agent]:
             cache_key = f"agent:{agent_name}"
 
             try:
-                agent = agent_loader.load_agent(agent_config, cache_key=cache_key)
+                # Wrap the agent config in the required top-level 'agent' key
+                wrapped_agent_config = {"agent": agent_config}
+                agent = agent_loader.load_agent(wrapped_agent_config, cache_key=cache_key)
                 agents.append(agent)
                 logger.debug("agent_name=<%s> | loaded agent for swarm", agent_name)
             except Exception as e: