Function flee 

pub fn flee(
    name: &str,
    agent_pos_key: &str,
    threat_key: &str,
    speed: f32,
    safe_distance: f32,
) -> BehaviorNode

Move the agent away from a threat position stored on the blackboard.

Reads:

• "{agent_pos_key}" — current agent position (Vec3)
• "{threat_key}" — threat position (Vec3)

Writes:

• "{agent_pos_key}" — updated position

Succeeds when the agent is more than safe_distance away.