nx_phototwin_gate.nx

nx_phototwin_gate.nx -- THE GATE FOR THE PHOTOGRAPH-TO-SUBSTRATE TWIN (nx_phototwin forked for real), 2026-08-24. FIXTURES ARE ASSEMBLED AT RUNTIME in /tmp/nx_phototwin_gate/: a 64x64 P6 PPM (a lossless container, so what the decoder returns IS what was written -- a tooth proves it) holding a grey ramp plus the pure sRGB primaries and secondaries, and a NARROW matrix/TRC ICC profile DERIVED from the mirrored sRGB2014.icc by pulling each primary halfway toward the white point (rXYZ' = rXYZ/2 + wtpt/6, so the three still sum to the white point -- the ICC structural invariant -- and nothing is typed in). The image is read through the sRGB profile in every run; the SUBSTRATE varies: sRGB itself = positive control (inside by construction: out_permil=0, moved=0), the narrow profile = the primaries are OUTSIDE and the proof must move them. That pair is the bite. The first version of this gate handed ONE profile to both roles and its narrow control was VACUOUS (measured 2026-08-24, out=0 on both). The wash ledger fixtures cover OK / FAIL / PARTIAL / EMPTY, and bench refuses partial coverage. license_tier: ORIGINAL No hw writes (Rule 26). expect_exit: 0