With items away from the window left off its board, a stub from the window
edge out to a rerouted net's far pin crossed copper the exact check never
saw: 38 shorts on th-eda's flight controller. A connection with an end
outside the bounds is now left unrouted, and a window whose new copper
leaves the window is refused.
A window's board now holds every pin and piece of copper of the nets it
reroutes and, of the rest, only items near the window, instead of the whole
board rebuilt per window. The smallest windows go first, at most
--window-cap per round (40), and no window starts once --window-budget of
the routing's own time is spent (0.25). On th-eda's flight controller the
stage had taken 12x the routing time for no gain.
After the exact engine, every net routed wholly inside a window around a
stuck connection's pins is ripped, the rest of the board is laid down as
fixed copper, and the window alone is routed again at --window-resolution
(default 4) with the stuck net and the ripped nets only. The result is kept
only if fewer connections are left unrouted; each round doubles the margin.
The grid and exact routers gain only_nets and bounds for it. Off by default.