G3 -- A match is byte-for-byte, and the whole binary still hashes

A function is matched only when its compiled output is instruction-identical to the original, register allocation included, AND the whole-binary hash check stays green with it linked. "Functionally equivalent" is never done. The hash check runs inside every build; there is no third state between "identical" and "failed". provenance: BFM G3 + the per-build SHA1 contract (Phase 5)