Sampler loop-end clamp: the Turtle Beach (Montego) short-envelope fix

A soundfont-importer off-by-one wrote loopEnd = sampleLen+1 on some switcher fonts (montego 19 zones, blackberry 9, diet_candy 6), so the sampler's buffer-end guard (pos >= src.length-1) fired BEFORE the loop-wrap could

• Fix, two layers: sampler.js clamps loopEnd = min(z.loopEnd, src.length-1) in BOTH the mixPCM (press/stream/bake) and live-native paths

▶ Play it: Ballroom Leviathan — a horn-and-piano genre that plays almost entirely sampled instruments https://stellate.app/?genre=bigband&seed=2550&path=814.14134,833.14167,795.14167&xdur=13.122

0399807 https://github.com/aboard-io/stellate/commit/0399807efd1a047bdf3db57c771cdc9428f68b5f