GM variety: use the whole palette — marimba/koto/dulcimer, not just winds

Paul: "use way more General MIDI — where are marimbas?? see how often we fall back on samples… we use so much of the same bases." We have 108 sampled instruments but the fallback (a synth-model voice remapped to a sample under sampledOnly) funneled almost every UNMAPPED generic synth…

• Widened SAMPLED_BASSES (+synth_bass_1/2), SAMPLED_PADS (+synth_strings_2/ atmosphere/fantasia/crystal/ice_rain), and every SAMPLED_LEAD family

• UNMAPPED generic synths now draw a lead family PER SONG across the whole palette (was always "wind"), so marimba/vibraphone/koto/dulcimer/accordion actually appear.

• RENDER-only (pickSampledId runs in forceSampled, not buildEvents) → fixtures 0-drift, matrix/segment-parity byte-identical; the instrument HEARD changes, the score does not.

▶ Play it: Ballroom Leviathan — a horn-and-piano genre that plays almost entirely sampled instruments https://stellate.app/?genre=bigband&seed=3311&path=814.14134,833.14167,795.14167&xdur=13.122

527dae3 https://github.com/aboard-io/stellate/commit/527dae3779df701306eff709b9a5693b2da74e67