fix(zh-CN): localize readouts and keep short labels intact

Preserve Chinese unit casing and spacing in the HUD and cockpit, localize FIRMS cache ages, CCTV health and radio counts, and keep imagery resolution and route modes readable. Add regression coverage for localized output and unchanged English.

Co-Authored-By: Codex (GPT-6) <[email protected]>

src/ui/cockpitContext.js

@@ -1,6 +1,6 @@
 /** Contact readouts and nearby-signal presentation for the Cockpit controller. */
 import * as Cesium from 'cesium';
-import { formatNumber, t, tn } from '../i18n/index.js';
+import { formatNumber, getLocale, t, tn } from '../i18n/index.js';
 import { unitLabel } from './unitLabels.js';
 import {
   bearingBetweenCoordinates,
@@ -15,7 +15,7 @@ const LOCALIZED_CONTEXT_SCOPE = Object.freeze({
   window: ({ label, radiusKm }) =>
     t('{label} · {radius} AIR/SEA WINDOW', {
       label,
-      radius: `${radiusKm === null ? '—' : formatNumber(radiusKm)}\u00a0${unitLabel('km').toUpperCase()}`,
+      radius: `${radiusKm === null ? '—' : formatNumber(radiusKm)}\u00a0${getLocale() === 'zh-CN' ? unitLabel('km') : unitLabel('km').toUpperCase()}`,
     }),
   installations: ({ scope, coverage }) =>
     t('{scope} · INSTALLATIONS {coverage}', { scope, coverage }),