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/ui/streetLevelPresentation.js

@@ -7,6 +7,7 @@ import {
   translateKnown,
 } from '../i18n/index.js';
 import { keyGuidanceText, keyRequirementText } from './keyGuidance.js';
+import { roundHeadingDegrees } from '../data/headingDegrees.js';
 
 // Street Level UI state to panel strings and flags. Pure, so it is testable.
 
@@ -175,9 +176,8 @@ function presentViewer(state) {
   const { street } = state;
   const right = [];
   if (street.isPano) right.push('360°');
-  // 359.5° and above rounds to north; modulo keeps it from printing 360°.
   if (Number.isFinite(street.bearing))
-    right.push(`${Math.round(street.bearing) % 360}°`);
+    right.push(`${roundHeadingDegrees(street.bearing)}°`);
   if (street.capturedAt)
     right.push(formatDate(street.capturedAt, street.capturedAtPrecision));
   const left = [];