Synth v2: modular pro layout, HOLD latching pads, fuller voice engine

- Modular hardware-style panel: System / Oscillator / Filter / Envelope
  / LFO / Drive / Echo / Output / Keyboard sections with labeled frames
- HOLD switch: pads become latching toggles (switching pads retunes the
  held note, unlatching or disabling HOLD releases it)
- Fuller Web Audio voice: waveshaper drive, full ADSR, feedback delay
  (time/feedback/mix), LFO target switch (cutoff or pitch via detune),
  octave/detune/glide with live retuning of held notes
- More of the library in service: MetalKnob (drive, with value bubble),
  VintageKnob (echo time), horizontal LEDFader (echo mix), XYPad
  two-way-linked with the cutoff/res knobs (exponential x-axis mapping),
  SegmentDisplay live frequency readout, 4 preset buttons that glide
  every knob via animateChanges
- Disambiguated synth aria-labels from gallery demos; octave readout
  fixed via decimals/format
- SteppedKnob now honors the format prop for numeric readouts

packages/dreamknob/src/skins/SteppedKnob.tsx

@@ -30,6 +30,7 @@ export const SteppedKnob = React.forwardRef<HTMLDivElement, SteppedKnobProps>(fu
   labelColor,
   label,
   showValue = true,
+  format,
   focusRing,
   className,
   style,
@@ -92,7 +93,11 @@ export const SteppedKnob = React.forwardRef<HTMLDivElement, SteppedKnobProps>(fu
                 fontWeight={600}
                 style={{ pointerEvents: 'none' }}
               >
-                {positions ? positions[index] : ctx.value.toFixed(ctx.decimals)}
+                {positions
+                  ? positions[index]
+                  : format
+                    ? format(ctx.value)
+                    : ctx.value.toFixed(ctx.decimals)}
               </text>
             )}
             {label && (