Constant QDRANT_DEFAULT_AGENT_ID 

pub const QDRANT_DEFAULT_AGENT_ID: &'static str;

V3 default agent_id payload value on Qdrant collections.

Qdrant does not maintain an agents table; it stores the agent alias directly as the agent_id payload field. The AgentScopedMemory wrapper’s must filter expects agent_id == "default" for the V1/V2 single-agent bridge.