nx_uxf_remux_gate.nx

nx_uxf_remux_gate.nx -- FM4: drives the EXTRACTED uxf_remux_frame and proves the rewrap is lossless. This is both the D001 migration of nx_uxf_remux_test and the proof that the extraction is faithful: the five original teeth are preserved in order and predicate, now asserted against the CALLABLE entry point rather than against logic inlined in a test. Three refusal teeth are added because the extraction introduced boundary checks, and a deny path that has never been shown to fire is not a guard. The positive control is T1 to T5 themselves: a well-formed element MUST be accepted, so a function that refused everything would fail them. license_tier: ORIGINAL No hw writes (Rule 26).