MEP-56 note 11: Testing gates

Author: research pass for MEP-56 (Mochi to Ruby transpiler). Date: 2026-05-29 (GMT+7).

Per-phase Go test functions in transpiler3/ruby/build/. vm3 oracle for byte-equal stdout diff. CRuby 3.2 + 3.4 + macos-latest matrix in CI. JRuby and TruffleRuby skip-gated when not in PATH. Tebako gate skip-gated when TEBAKO_HOME not set.

Full research note content for MEP-56 note 11.