Propose one run per box, in roster order, non-overlapping.
Each accepted run LEAVES THE FREE SET before the next box is placed, so two boxes appearing
together are never offered the same channels — the proposal is one answer about the whole
roster, not a per-box answer computed in ignorance of its neighbours.
A GHOST is skipped entirely: it is a departed box drawn so its patches can be reached, never a
device to patch ONTO. So is a box with no inputs side. Neither is a refusal — there is nothing
to place, which is a different fact from "it does not fit".
Propose one run per box, in roster order, non-overlapping.
Each accepted run LEAVES THE FREE SET before the next box is placed, so two boxes appearing together are never offered the same channels — the proposal is one answer about the whole roster, not a per-box answer computed in ignorance of its neighbours.
A GHOST is skipped entirely: it is a departed box drawn so its patches can be reached, never a device to patch ONTO. So is a box with no inputs side. Neither is a refusal — there is nothing to place, which is a different fact from "it does not fit".