A pickup record needs the handoff method

Source trail note for distinguishing buyer pickup, proxy pickup, desk receipt, and locker events.

The phrase "picked up" hides too much. A buyer pickup, roommate pickup, front-desk receipt, locker open event, and courier scan are different records. They answer different disputes. For a useful source trail, I would store the handoff method before storing a long explanation. That one field changes how later readers interpret the proof.