Add a Tracked trait and a Lookahead harness to common-dsp. Each engine is
now its tracker plus a module that follows note events aligned with its
input, so the same module can run behind a shared tracker.
Lathe and Temper output is bit-exact against the old engines. Knurl's
interpolation now reads one newer sample inside the module, so its
latency is one sample longer; the output matches within float rounding.
Each editor exposes body() and toggles() besides show(), so another
editor can draw a module's page.
Knurl follows the played note and treats every cycle of the wave on its
own: a repeating level pattern over 1-16 cycles makes subharmonics in tune
with every note, random level and timing per cycle add rattle, and a noise
burst per cycle, highpassed at a multiple of f0, adds grit. Amounts are
counted in cycles, so the texture is the same on F1 and on C2.
- Cycle clock from the shared note tracker, restarted at each note; the
audio is delayed by the lookahead plus 4.2 ms of timing-jitter headroom.
- Per-cycle randomness from a hash of the cycle number: Same every note
or Free.
- Patterns Off, Double, Triple, Fry (default), Gallop, Stutter or drawn;
grit switchable per step. Pattern persisted as knurl-pattern.
- Editor: last eight cycles overlaid, pattern bars with the playing step.
- Tests match the prototype: Double gives f0/2 at -8.19 dB, Triple f0/3
at -10.68 dB, equal on F1 and C2, no added clicks, bit-exact when off,
no allocation on the audio thread.
nvrl