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.

scripts/format-scope.json

@@ -1180,5 +1180,6 @@
   "src/testSupport/hudReadouts.mjs",
   "src/ui/stores/firstRun.js",
   "src/firstRunLauncherView.test.mjs",
-  "src/firstRunCopy.js"
+  "src/firstRunCopy.js",
+  "src/data/headingDegrees.test.mjs"
 ]