nx_ltv_gate.nx

nx_ltv_gate.nx -- INDEPENDENT GATE: PAdES levels + the three-valued verdict (crown teeth). Proves the two things that decide whether an old signature survives: (1) an expired-certificate signature is INDETERMINATE, NEVER INVALID -- opposite legal outcomes, and calling it invalid impeaches a validly-signed document; (2) B-LT and up still verify PAST expiry because the revocation proof travels inside the file, whereas a chain WITHOUT revocation data is only B-T (the half-measure that looks archival and is not). WRITE BUDGET (debt 1785519597): reg_put is disk-bound at ~0.7s+ under NAS I/O contention; reg_get is ~70us. One signature, upgraded one component at a time, FIVE writes, unlimited free assertions. license_tier: ORIGINAL No hw writes (Rule 26). expect_exit: 0