Wire scratch to FIRE: turntablist genres get the fwd↔back hand (A.1)

The f.scratch DSP capability landed opt-in/silent last session; this makes it play. Deterministic + occasional, biased to turntablist genres, byte-safe when absent (a dedicated +7333 rng stream never drawn unless a genre opts in).

• csd-engine: stamp scratch on chops-role hits (crateflip's soul-78 chops) and ONLY the break-role stutter ornament (boombap/jungle amen) so the drum groove stays intact; carry scratch onto srcById conditionally.

• state-engine: plumb scratch through the chop push -> found-player sees f.scratch.

• found-player: the real-time FoundLive.chop pre-renders the triangle scrub into a one-shot buffer (WebAudio has no scrub primitive), same math as mixPCM.

• genre-kernel: foundScratch pulled from the found parent; scratch key baked onto opted sources only. crateflip 0.18 (chops), boombap 0.5 / jungle 0.45 (stutter).

▶ Play it: Barometric Stampede → Milk Crate Scripture → Shellac Excavation — the three genres this change names, as one path https://stellate.app/?genre=jungle&seed=4466&path=1718.20526,205.10395,90.9508&xdur=0.067

fd145a3 https://github.com/aboard-io/stellate/commit/fd145a3a97ce097e4b31f719864be59892c1ecd5