Two fixes driven by user reports:
1. MLP wasn't affecting the sound. Matrix cells are now opt-in to the
MLP output vector rather than always-driven. Default modular paramMeta
is 32 mod-source params (4 ADSR * A/D/S/R + 8 LFO * rate/morph), down
from 512. The default patch's MM_Matrix/s00_d08_amp=1.0 now survives
the first inference tick because it's not in paramMeta — ADSR1 stays
routed to amp and the MLP drives envelope shape per joystick position.
Matrix cells still clickable as direct-DSP knobs in modular-ui: setCell
now routes through engine._setRawByLabel(). A later UI pass can add a
"expose to MLP" menu entry that calls engine.setExposeMatrixCell(s,d).
Also removes the earlier exampleCount-based routing gate; no longer
needed now that the default patch is stable.
2. Per-group curve drawer (hover over section labels on the synth
visualizer) is now available for all synth engines, not just C15.
Refactored showGroupDrawer behind a getSectionView(sectionIndex)
helper that returns a uniform view for either C15 (via SYNTH_SECTIONS
+ groupOverrides) or non-C15 (via nonC15Sections + nonC15GroupCurves
+ engineParamOverrides).
Group-level curve persists across sub-engine swaps by group name, so
e.g. tuning the "ADSR 1" curve survives a switch between subtractive
and fm without being reset.
ModularEngine: adds setExposeMatrixCell(s,d,exposed) +
getExposedMatrixCells() + clears exposed cells on sub-engine swap.
4507db00c8