Idle agents now live a little: after settling in they occasionally walk the
lane graph to the coffee machine, snack counter, or a restroom stall, dwell
there, and stroll back - carrying their coffee or snack to the desk for a
while. Working agents never leave, and an agent woken to work mid-break
abandons the trip and heads straight home. Randomness is injected so the
whole loop - trip, dwell, carry-back, interruption - is deterministic under
unit test, and a settle period keeps the floor calm right after it loads.