sf2 extract: FULL CAPTURE — every key-zone + every velocity layer

Paul: "re-extract the soundfont fully, capture everything." zonesOf kept only the forte layer (vel~100) and extract thinned to --max-zones 6. Now zonesOf keeps EVERY velocity layer (records velLo/velHi), and extract defaults to no thinning (--max-zones 0 = full capture

• Validated: UprightPianoKW -> 66 zones across BOTH velocity layers (0-80 soft, 81-127 loud, previously the soft layer was discarded); FluidR3 Yamaha Grand -> all 20 key-zones (was 6).

• This is the extract side only. Consuming it needs the kernel INSTRUMENTS block regenerated from the fuller zones.json (velLo/velHi added) + the native sampler selecting a zone by velocity, not just note

▶ Play it: Ballroom Leviathan — a horn-and-piano genre that plays almost entirely sampled instruments https://stellate.app/?genre=bigband&seed=5049&path=814.14134,833.14167,795.14167&xdur=13.122

8b13bae https://github.com/aboard-io/stellate/commit/8b13bae10203105cb5a66153eff96481fe1f9de0