4633e570e8
The previous commit f4bee44 updated AgentService.cs but missed
OpenClawGatewayClient.cs which also reads agent IDs and model config
from the raw openclaw.json. Both LoadAgentIdsFromConfig() and
GetAvailableModels() now default to /etc/nexus/agents-sanitized.json.
This completes the P4 migration: Nexus no longer needs read access to
openclaw.json for any code path.