Audit fixes: a11y, gesture correctness, math edge cases

- Keyboard focus-visible ring on all controls (WCAG 2.4.7), suppressed
  for pointer grabs; focusRing prop to customize or disable
- aria-orientation on track modes; data-dragging/-disabled/-readonly/
  -focus-visible state attributes; disabled dims, readOnly drops the
  grab cursor
- Escape cancels a drag and restores the pre-gesture value
- Controlled mode no longer desyncs when the parent rejects onChange
- Second concurrent pointer can no longer hijack a drag session;
  drags cancel when disabled/readOnly flips mid-gesture
- Wheel: onChangeStart symmetry, settle flush on unsubscribe, dominant-
  axis direction (fixes macOS Shift+scroll reversal), ignored mid-drag
- Shift+wheel and fine multipliers now work on stepped/values knobs
- Fader/LEDFader track mapping inset-aligned with handle travel (no
  value jump when grabbing the cap); LEDFader zones sorted
- roundTo no longer returns NaN for exponential-notation values;
  logTaper falls back to linear for invalid ranges; decimalsFromStep
  shaves float noise; findClosest([]) returns the input
- Double-click reset brackets with onChangeStart/End
- MetalKnob honors showValue/unit/format; VintageKnob omits them from
  its type; TickLabels extracted as a public primitive
- SegmentDisplay: letters/hex charset, dash overflow instead of 888

packages/dreamknob/src/components/Knob.tsx

@@ -6,6 +6,11 @@ import { useKnob } from '../hooks/useKnob';
 export interface KnobProps extends KnobCoreProps {
   /** Square canvas size in px. Default: 80. */
   size?: number;
+  /**
+   * Color of the keyboard focus ring, or `false` to disable it (only do this
+   * if you render your own focus indicator). Default: a soft blue.
+   */
+  focusRing?: string | false;
   className?: string;
   style?: React.CSSProperties;
   /** SVG children (Arc, Pointer, Ticks, ...) or a render function receiving the live state. */
@@ -21,6 +26,7 @@ export interface KnobProps extends KnobCoreProps {
  */
 export const Knob: React.FC<KnobProps> = ({
   size = 80,
+  focusRing = 'rgba(130,180,255,0.65)',
   className,
   style,
   children,
@@ -52,6 +58,10 @@ export const Knob: React.FC<KnobProps> = ({
           position: 'relative',
           width: size,
           height: size,
+          borderRadius: '50%',
+          ...(knob.isFocusVisible && focusRing
+            ? { boxShadow: `0 0 0 2px ${focusRing}` }
+            : undefined),
           ...knob.bind.style,
           ...style,
         }}