Round every heading readout through one shared helper

The transit, ALPR, vessel, CCTV and flight/military context fixes each
wrapped 359.5° to north with an inline Math.round(x) % 360. They now call
roundHeadingDegrees in src/data/headingDegrees.js, which also wraps negative
and multi-turn bearings. normalizeHeading moves there with it, and
cockpitMath re-exports it so existing imports keep working. It now adds a
turn only to a negative remainder, so a bearing just under half a degree
keeps its precision.

The awareness, Local ADS-B, cockpit wind, cockpit heading and Street Level
readouts use the same helper. The Cockpit's TRACK ACQUIRED signal rounded
without wrapping and could read COURSE 360°; it now uses
formatHeadingReadout, which shows --- for a track that is not finite.

src/cockpitMath.js

@@ -1,10 +1,10 @@
-export { resolveHudRailLayout } from './ui/panelRailGeometry.js';
+import {
+  normalizeHeading,
+  roundHeadingDegrees,
+} from './data/headingDegrees.js';
 
-/** Normalize a heading into the [0, 360) range. */
-export function normalizeHeading(value) {
-  if (!Number.isFinite(value)) return 0;
-  return ((value % 360) + 360) % 360;
-}
+export { resolveHudRailLayout } from './ui/panelRailGeometry.js';
+export { normalizeHeading };
 
 /**
  * Three-digit heading readout, 000–359.
@@ -12,7 +12,7 @@ export function normalizeHeading(value) {
  */
 export function formatHeadingReadout(degrees) {
   if (!Number.isFinite(degrees)) return '---';
-  return String(Math.round(normalizeHeading(degrees)) % 360).padStart(3, '0');
+  return String(roundHeadingDegrees(degrees)).padStart(3, '0');
 }
 
 /** Advance a displayed heading along the shortest arc without exceeding a slew rate. */