Dash: DIN 1451 opt-in per widget (hudFont), GNSS compass, rei by default; widget catalogue

From smart-serow: the DIN 1451 face (Alte DIN 1451 Mittelschrift, via gps-speedo)
and GpsCompass. A cosmetic font is opt-in: widgets name hudFont in their own
TextStyle, the rest keeps the basic font (CJK). Boxes and telltales shrink long
labels instead of wrapping. Telltale and Reading get their own files;
lib/README.md catalogues folders and widgets like smart-serow's.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DDwfd6Ki8UfG4hK6W5YpJz

lib/reading.dart

@@ -0,0 +1,28 @@
+// One signal's current state as a display needs it: value, and whether to draw it dim
+// (missing, stale or known-without-value; app guideline 2).
+
+import 'boundary.dart';
+
+/// One signal's current state, as the dash needs it.
+class Reading {
+  const Reading(this.value, {this.dim = false});
+
+  /// The value, or null when missing or known-without-value.
+  final Object? value;
+
+  /// Missing or stale: drawn in subdued.
+  final bool dim;
+
+  static Reading of(Boundary b, String name) {
+    final e = b.signals[name];
+    if (e is! Map) return const Reading(null, dim: true);
+    final q = e['quality'] as String? ?? 'ok';
+    return Reading(e['value'], dim: q != 'ok' || e['value'] == null);
+  }
+
+  double? get number => value is num ? (value as num).toDouble() : null;
+  bool get on => value == true;
+
+  String fixed([int decimals = 0]) =>
+      number == null ? '—' : number!.toStringAsFixed(decimals);
+}