Supersaw lead + pulse kit + humanized fills

Engine (all defaults preserve existing renders byte-for-byte paths):

• melody voices/spread params: 3+ voices generates a detuned unison stack (supersaw); <=2 emits the original two-osc code.

• melody pattern "hero": 16th runs, syncopation, octave leaps, A/B phrase variants alternating per chord

• drum kit "pulse": four-on-floor + per-chord wandering ghost snares, alternating push-kick, accented 16th hats

• tom fill takes the song rng: flams, optional extra 8th, final roll resolves straight-16ths or triplet — every fill in a song differs

▶ Play it: Ballroom Leviathan — a horn-and-piano genre that plays almost entirely sampled instruments https://stellate.app/?genre=bigband&seed=5241&path=814.14134,833.14167,795.14167&xdur=13.122

b838638 https://github.com/aboard-io/stellate/commit/b83863897ee51f36dac7620577a93e80ce286884