nx_retire_onto_gate.nx

nx_retire_onto_gate.nx -- GATE for retire-onto-owner (global tooling, 2026-08-24). Composes the lib in-process. FIXTURES: the differential PROBE imports the candidate and the owner BY BASENAME through the estate's own builder, so the fixtures must live where that resolver looks -- the corpus root the gatekit resolves (<X>/runtime/). They are named _ro_fixture_* so any reader recognises them as transient, written at SETUP and removed at the end (and at setup, so a crashed prior run cannot poison this one). The sweep fixture plane and the scratch live in /tmp/nx_retire_onto_gate/. THE ANTI-VACUITY TOOTH: the fixture body carries a `}` inside a LINE COMMENT and a `}` inside a STRING LITERAL. A naive brace matcher ends the body at the first of those, leaves the rest of the old body behind the new closing brace, and the file still LOOKS rewritten -- so the tooth asserts the leftover Newton loop is GONE. THE PROOF TEETH: prove against a true floor-sqrt owner PASSES; against an IDENTITY owner with the same signature it must report SEMANTICS-DIFFER (the signature-only rewrite would have silently changed behaviour); an unbuildable candidate must report UNBUILDABLE; a two-argument function must report UNSUPPORTED. Every refusal leaves the bytes untouched, and apply writes ONLY after a PASS.