nx_av1_dct_gate.nx

nx_av1_dct_gate.nx -- proves the inverse DCT networks by STRUCTURAL property. Reference bit-exactness needs libaom's test vectors, which are not present here. What IS provable without them is the set of properties a correct DCT basis must have and a mis-wired one cannot fake: T1 DC-only in -> FLAT out. Any butterfly wired to the wrong index or any sign error in the even path breaks this immediately. T2 odd basis index -> ANTISYMMETRIC out (out[i] == -out[n-1-i]). This is what catches a wrong rotation angle in the odd path. T3 even basis index -> the specific symmetric pattern. T4 LINEARITY within rounding slack. A network that is structurally right but uses a halved angle still passes T1; it does not survive T2 plus the basis-frequency check in T5. T5 the constants land where the angle mapping says: cospi_16_64 is cos128(32) = 2896, not cos128(16). Halving the factor yields a transform that still LOOKS like a DCT and decodes blurred. This gate does NOT claim bit-exactness against libaom. It claims the network is structurally a DCT with the right frequencies. license_tier: ORIGINAL