57 new tests in test_audio_sprint13.gd covering bus setup, dip profiles, zone crossfade, recognition chime, and murmur wiring. Fix lambda capture bug in 3 signal tests (String → Array wrapper for reliable closure capture in Godot 4). Add bus volume reset to before_test() for test isolation against prefs-loaded state. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>