Found-at-90%: the vocal/chop/bed layer only plays at a dominant genre

Paul: "whatever vocal or sampled chops and found sound beds are in use stop playing unless a genre is at 90% or above." The found layer now renders only when the top blend weight >= 90% (genreMeta.t <= 0.1)

Verified: fixtures 0-drift; vaporwave found events = 10 at t=0/0.05, 0 at t=0.3.

▶ Play it: Food Court Eternity — parked on the genre this change names https://stellate.app/?genre=vaporwave&seed=9792&path=1679.4393,1698.4426,1660.4426&xdur=13.122

c572b82 https://github.com/aboard-io/stellate/commit/c572b820aaf08fcadef280bdb5810576bf323ca6