rooms_shove_channel is the headline density win: a sealed NET_A wall
leaves no top<->bottom door, so plain room routing drops NET_C; with
shove=True NET_A is nudged aside and both nets route, DRC-clean and
deterministic. rooms_wide_door seats two nets through one wide gap at
distinct projected gate points with no shove.
Cover the occupancy-aware projection math directly, assert the four
foundation fixtures stay byte-identical under shove=True (shoves==0), and
extend the room DRC-clean parametrize with both new fixtures.
Adds narrow_channel.dsn: a keepout wall with a narrow gap positioned off the
routing grid, so no grid cell centre falls inside the gap's free centreline.
The exact/grid track drops the net (cell quantization can't fit a centreline
in the channel); the continuous room track routes it. This is the headline
result that continuous free-space beats the grid.
Tests: the room router's output is DRC-clean (exact has_violation is None) on
simple/crossing/kicad/narrow_channel; it connects simple/crossing (with a via)
and all four multi-pin KiCad nets; traces are orthogonal and end on pads; and
the continuity contrast asserts exact routes 0 while rooms routes 1, both
clean. Oracle-gated connectivity parity on simple/crossing.
