nx_comparetree_lib_gate.nx

nx_comparetree_lib_gate.nx -- the referee for the two-tree /compare resolver (nx_comparetree_lib). WHAT MAKES THIS GATE REAL RATHER THAN DECORATIVE: * IN-PROCESS. It imports the lib and calls it directly, so nx_gate_bite can mutate the lib and watch this go RED. A gate that fork/execs a deployed elf reports NOT-REACHED for every mutant and its GREEN proves nothing about the code under test. * REAL FILES, NOT A SIMULATION. The three resolution cases are exercised against actual fixture files under /tmp/<gate>/, because the defect being guarded is a FILESYSTEM LOOKUP. A gate that only tested the pure decision would pass while the resolver read the wrong path. * THE FIXTURE IS ASSERTED BEFORE THE OUTCOME. If the fixture write failed, every "resolves to secondary" tooth below would pass for the wrong reason -- an absent file resolves nowhere. * ANTI-VACUITY BY CONTENT. Each case checks the BYTES RETURNED, not just the which-tree flag. A trivial implementation that always sets the flag to PRIMARY and reads nothing cannot pass, and that implementation is kept here as cg_wrong_pick so the claim is demonstrated, not asserted. * cwd-INDEPENDENT. Fixtures are absolute and the production-order teeth compare constants, so this gate cannot pass or fail because of where a runner happened to start it. license_tier: ORIGINAL