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/digital/segments.tsx

@@ -22,9 +22,41 @@ const CHAR_SEGMENTS: Record<string, SegmentKey[]> = {
   '8': ['a', 'b', 'c', 'd', 'e', 'f', 'g'],
   '9': ['a', 'b', 'c', 'd', 'f', 'g'],
   '-': ['g'],
+  '_': ['d'],
+  '=': ['g', 'd'],
   ' ': [],
+  // Letters, as far as seven segments allow — enough for hex, "OFF", "On",
+  // "LP"/"HP", "Err", "dB" and friends.
+  A: ['a', 'b', 'c', 'e', 'f', 'g'],
+  b: ['c', 'd', 'e', 'f', 'g'],
+  C: ['a', 'd', 'e', 'f'],
+  c: ['d', 'e', 'g'],
+  d: ['b', 'c', 'd', 'e', 'g'],
+  E: ['a', 'd', 'e', 'f', 'g'],
+  F: ['a', 'e', 'f', 'g'],
+  G: ['a', 'c', 'd', 'e', 'f'],
+  H: ['b', 'c', 'e', 'f', 'g'],
+  h: ['c', 'e', 'f', 'g'],
+  I: ['b', 'c'],
+  J: ['b', 'c', 'd'],
+  L: ['d', 'e', 'f'],
+  n: ['c', 'e', 'g'],
+  O: ['a', 'b', 'c', 'd', 'e', 'f'],
+  o: ['c', 'd', 'e', 'g'],
+  P: ['a', 'b', 'e', 'f', 'g'],
+  q: ['a', 'b', 'c', 'f', 'g'],
+  r: ['e', 'g'],
+  S: ['a', 'c', 'd', 'f', 'g'],
+  t: ['d', 'e', 'f', 'g'],
+  U: ['b', 'c', 'd', 'e', 'f'],
+  u: ['c', 'd', 'e'],
+  y: ['b', 'c', 'd', 'f', 'g'],
 };
 
+/** Resolve a character to its segments, trying the other case before giving up. */
+const segmentsFor = (ch: string): SegmentKey[] =>
+  CHAR_SEGMENTS[ch] ?? CHAR_SEGMENTS[ch.toUpperCase()] ?? CHAR_SEGMENTS[ch.toLowerCase()] ?? [];
+
 const H_HALF = 1.1; // half thickness
 const INSET = 0.45; // gap between adjacent segments
 
@@ -78,7 +110,7 @@ export const renderSegmentText = (
       );
       continue;
     }
-    const lit = new Set(CHAR_SEGMENTS[ch] ?? []);
+    const lit = new Set(segmentsFor(ch));
     const digit: React.ReactNode[] = [];
     (Object.keys(SEGMENT_POINTS) as SegmentKey[]).forEach(seg => {
       const on = lit.has(seg);
@@ -117,6 +149,8 @@ export const formatForDisplay = (
 ): string => {
   let text = value.toFixed(decimals);
   const cellCount = (s: string) => s.replace(/\./g, '').length;
-  if (cellCount(text) > digits) text = ''.padStart(digits, '8'); // overflow
+  // Doesn't fit: dashes, the hardware overflow convention. All-8s would read
+  // as a legitimate value.
+  if (cellCount(text) > digits) text = ''.padStart(digits, '-');
   return text.padStart(digits + (text.includes('.') ? 1 : 0), ' ');
 };