New engine movements/strafe.nim, selected by TR_MOVEMENT=strafe (default stays
tfil, byte-identical — test_tfil_commit_env.nim's 30 checks still pass).
Design (the owner's):
- AXIS = incoming bullet's direction when a bullet is in flight, else the
perpendicular of the enemy bearing. The body heading is kept inside a band
(TR_STRAFE_BAND, default 20 deg) around the perpendicular LINE; it turns only
when outside the band, and never turns to face a movement target.
- Candidate tiles on the perpendicular line through our position, both forward
and backward, within TR_STRAFE_REACH px, with a perpendicular jitter of
+/- TR_STRAFE_SPREAD tiles. A tile is acceptable when its path max heat is
<= PathDangerThreshold, the SAME safety rule TFIL uses.
- Move by SIGN only: setForward(+/-MaxSpeed>). Dwell is re-picked after a random
number of ticks in [TR_STRAFE_DWELL_MIN, TR_STRAFE_DWELL_MAX], on arrival, or
on a serious threat spike.
- Heat machinery is REUSED from the shipped mover, not re-implemented: the
exported heatDecay()/bulletMagScale() (j105 time-indexed model) and the
PillarHotness/PillarRadiance globals (j106 pillar-free default). The heat
shape is overridable via TR_STRAFE_CORRIDOR_HEAT/WALL_HOTNESS/WALL_RADIANCE
(defaults = the shipped TFIL field).
- GUI overlay: strafe line, threat axis, candidate tiles (safe/unsafe), chosen
target, sign-coloured movement ray, and the heading band.
Gates (offline, recorded DrussGT fixture, 20026 ticks):
- A TILE AVAILABILITY: shipped heat field -> a safe tile exists on only 36.6%
of picks (63.4% fall back to the least-hot tile); the ring retune
(corridor 5, wall 10/5) raises it to 91.9%.
- B PREDICTABILITY: reversal-interval entropy 5.84 bits vs TFIL 5.09; direction
entropy 1.00 both; long-lag autocorrelation ~0 for both (no periodic
component). Fewer reversals (710 vs 1453) and more full-speed ticks.
measurements: common_libs/tests/measure_strafe_gates.nim
Also registers TR_STRAFE_* in the boot env report (ModularBot_garage/src/
env_report.nim) and wires the engine into ModularBot.nim (hold -> strafe,
ram trigger -> rammer).
