feat(i18n): presentation extraction — t() call sites, data-i18n templates, locale selector

Route every application-owned presentation string through the i18n
core: t() call sites across the app/layers/ui/data/voice surfaces,
data-i18n* attributes in the src/ui/templates/*.html markup (applied at
boot by applyDocumentTranslations from src/standalone/application.js),
and the dock locale selector (runtime-rendered from the offered pair —
a single EN button while only English ships).

Rebased onto current main, where the extraction follows the module
splits: the shell wiring now lands in the owner modules
(panelChrome, visualSettings, locationNavigation, shareRestoration,
shellFeedback, applicationShell) and the voice status corpus in the
realtime* modules; scene status lives in director.js +
playbackAdapter.js.

Modules shared with the node runtime (loadingFeedback,
installationFeedback, regionalModel, keySetupCore, vessels ingestion)
stay environment-neutral English and localize at their browser render
sites (chip maps in shellFeedback/installations controls, the weather
table in cockpitBriefing, keySetupRequirementEnvVars compositions), so
the package-boundary graph stays clean; the browser boundary groups
now own the i18n modules they reach (scripts/package-boundaries.json).

src/mapStackChips.js

@@ -10,7 +10,8 @@
 // state is re-synced from controller state (never optimistically), so a failed
 // or superseded switch still leaves the truly-active stack lit.
 
-import { keySetupRequirement } from './keySetupCore.mjs';
+import { keySetupRequirementEnvVars } from './keySetupCore.mjs';
+import { t } from './i18n/index.js';
 
 export const MAP_STACK_CHIP_CLASS = 'map-stack-chip';
 export const PRESENTED_MAP_STACK_IDS = Object.freeze([
@@ -37,9 +38,15 @@ export function mapStackChipModel(stack, activeId) {
   const available = stack?.available !== false;
   const label = String(stack?.label ?? stack?.id ?? '');
   const requiresIon = stack?.requiresIon === true;
+  // Stack labels are provider/dataset names (keep-English); the availability
+  // sentence around them is copy and localizes here at the model boundary.
   const fallbackReason = requiresIon
-    ? keySetupRequirement('cesium-ion')
-    : `${label || 'This map stack'} is unavailable`;
+    ? t('setup.keySetup.requirement', {
+        envVars: keySetupRequirementEnvVars('cesium-ion'),
+      })
+    : t('setup.mapStack.unavailableReason', {
+        label: label || t('setup.mapStack.fallbackName'),
+      });
   const unavailableHint = available
     ? ''
     : String(stack?.unavailableReason || fallbackReason);
@@ -119,7 +126,10 @@ export function renderMapStackChips(
     if (!model.available) {
       chip.setAttribute(
         'aria-label',
-        `${model.label} unavailable: ${model.unavailableHint}`,
+        t('setup.mapStack.unavailableAriaLabel', {
+          label: model.label,
+          hint: model.unavailableHint,
+        }),
       );
     }