Many fixes

[catfact]

• no longer requires 2^N frames buffer
• record offset initialized more correctly (doesn't glitch at non-integer write speeds), and can't be modulated (it's more dangerous than useful.)
• silence output when play is disabled
• clamp rate to +/- 32 so it doesn't crash Max
• clamp SVF freq to 1/2 nyquist so it doesn't explode
• update filter with per-sample rate change
• fix filer modulation algo.

still TODO:

• make a much nicer actual help patcher
• phase output. dunno if this should be a second audio signal (unquantized, like groove~ sync), or a message outlet that bangs when quantized phase updates (like norns poll)
• filter modulation helps with aliasing, but sweeping through zero rate (while writing) still causes rate spike that feels like a mistake (when playing back.) fix this with write-amplitude dead zone around rate==0.
• soft clipper function returns -0 always. no idea why (it works on the norns and the math looks fine.) disabled for now.