Read gfx_sp_tri1 against D233/D106/D271's existing guards. D233's
trivial-reject fix is ruled out as a direct cause -- GL clips well-formed
clip-space geometry correctly downstream of it. Found a new, previously
uncatalogued unguarded site: the G_CULL_BOTH backface-cull cross-product
divides raw vertex w with no epsilon guard, which can NaN/Inf near w=0
and silently skip both cull branches. Not yet confirmed against a live
repro. Added GE_D288 (cached-getenv, D250-safe) to catch the culprit
triangle's w/bbox at draw time on the next -level_20 run.
No game-logic change; port/fast3d/ diagnostic only, inert unless
GE_D288 is set.
James Dansereau
fbc2a533ae