Function move_to 

pub fn move_to(
    name: &str,
    agent_pos_key: &str,
    target_key: &str,
    speed: f32,
    arrival_radius: f32,
) -> BehaviorNode

Move an agent toward a 3-D target stored on the blackboard.

Reads:

• "{agent_pos_key}" — current agent position (Vec3)
• "{target_key}" — target position (Vec3)

Writes:

• "{agent_pos_key}" — updated position after movement this tick

Succeeds when the agent is within arrival_radius of the target. Returns Failure if either position key is absent.