nx_boundscheck_constidx.nx

nx_boundscheck_constidx.nx -- STANDING WITNESS for the COMPILE-TIME leg of LN3 raw-pointer provenance (sibling of nx_boundscheck.nx; same family as nx_litprobe / nx_constidx_probe). buf[64] on a 64-byte allocation is a provable out-of-range access. Under the DEFAULT build this compiles clean and runs (reading one byte of neighboring memory -- the silent C-class behavior, kept as the hazard record). Under `--ptrprov` the compiler REFUSES it at parse time with the 5W+H provenance diagnostic -- nx_boundscheck_gate asserts both directions and that the refusal names the provenance rule, not some other error. license_tier: ORIGINAL No hw writes (Rule 26).