nx_vnsprite_gate.nx

nx_vnsprite_gate.nx -- liar-kill gate for the VN sprite compositor (gamebench bit 13). T1 Z-ORDER is real: at an overlap the higher-z layer's pixel wins; swapping z swaps the winner. T2 ALPHA + KEY are exact: a 50% blend lands on the exact integer mix per channel, and a key-color pixel is fully transparent (background shows through untouched). T3 CLIPPING cannot write out of bounds: blits hanging off every edge leave 8 canary cells intact. T4 EXPRESSION SWAP IS VISIBLE: base+smile vs base+frown differ in >=20 pixels; recomposing the same expression twice differs in 0 (visible AND deterministic -- the VN beat that matters). T5 SCENE STATE ROUND-TRIPS: the layer table through gs_save -> ZEROED -> gs_load -> recompose is frame-checksum identical (parts doctrine: everything persists through the save part). T6 DETERMINISM: the full scene composed twice is checksum-identical. T7 ANTI-VACUITY: the composed scene differs from the bare background in >=500 px with >=5 distinct sprite colors (a compositor that draws nothing cannot pass). T8 SCENE ARTIFACT: a full VN frame (gradient bg + two characters + alpha textbox + name tag) is written as a sovereign PNG to knowledge/nx_vnsprite_scene.png -- the board's evidence. T9 GROUP EXCLUSIVITY (the Ren'Py layeredimage bar, researched 2026-07-29): smile and frown are two attributes of ONE group; a single vsp_setg call swaps them with no manual bookkeeping, and exactly one is ever composed (probed at pixel level both ways). T10 DISSOLVE EXACT: the core VN transition -- t=0 equals frame A, t=256 equals frame B (full-frame checksums), and the t=128 midpoint is the exact integer channel mix at a probed pixel. license_tier: ORIGINAL expect_exit: 0