scene_probe prints the grid s size, its walkable count, the count reachable from
where the fly stands and the count never stood on, draws the ground with the
reading it actually used, and names the refusal when there is no grid. trap_hunt
carries the same line into every trace line and into the summary, so a stalled
walk can be read at a glance: a fly with 719 walkable tiles and 4 reachable ones
is fenced in and no re-plan will help it.
A scene histogram says "battle" and a battle deals five different pads
(docs/design/macros.md 12.6, 13.1), so a loop inside one of them is
invisible in the tables the hunt already prints. Three more: frames per
sub-state, every macro channel ever bound in each one, and the macro
starts by the sub-state they started on.
