nx_gamemusic.nx

nx_gamemusic.nx -- the SOVEREIGN MUSIC/SEQUENCER PART, completing the `audio-sfx-music` capability. nx_game_audio_gate already PROVES the SFX half (nx_audio_sfx + nx_audio_wav: coin/laser/explosion, real WAV + waveform, 3/3 GREEN) and says in-band that audio "needs WIRING to games". What was genuinely missing was MUSIC: nothing turned a SONG into audio, so claiming the full capability would have been an overclaim on the strength of the SFX gate alone. COMPOSES rather than rebuilds (DRY / no-proliferation law): note oscillation reuses `sfx_tone` from nx_audio_sfx, output reuses `wav_render_stereo`/`wav_save` from nx_audio_wav. This part adds only what was absent -- pitch, envelope, sequencing and mixing. CERTIFIED PROPERTIES (each a gate tooth): 1. EXACT INTEGER EQUAL-TEMPERAMENT. Pitch comes from a 12-note table with octave shifts by doubling or halving, so A4=440 -> A5=880 is EXACT. No float, no pow(), no drift between builds or machines. 2. DETERMINISTIC RENDER -- the same song data yields byte-identical audio, so a soundtrack is reproducible and diffable (the determinism exceed, carried into audio). 3. DATA-DRIVEN SONGS (rule 11) -- a song is an array of (semitone, octave, ticks); melodies are DATA, never code. Rest is encoded as semitone -1. 4. SATURATING MIX -- layering tracks cannot wrap the sample and produce the click/crack of integer overflow; it clamps at the sample ceiling instead. 5. PER-NOTE ENVELOPE -- notes attack and decay rather than clicking on/off at full amplitude. LIB ONLY -- no main() by ecosystem convention. license_tier: ORIGINAL expect_exit: 0