Switch language in place, without a reload

Choosing a language in the picker now applies it at once. The choice is
stored and ?lang is kept in step through replaceState, and the picker keeps
focus.

Code that writes translated text itself re-presents it on a switch:
onLocaleChange() lets an owner listen, removed at teardown, and status
writers hand over a function of the locale (voice cards, scene director,
SDR, draw hints, imagery split, map sources, Bhote Koshi media) so the
words are rebuilt rather than re-sent. The HUD, cockpit, radio, CCTV,
launch, awareness and credit texts follow the same hook, and
applyDocumentTranslations can be applied again without undoing text code
wrote since.

The unsaved-work registry and persistLocaleAndReload existed only to guard
the reload, so they go, with their catalog entries.

src/ui/imagerySplit.js

@@ -1,3 +1,4 @@
+import { onLocaleChange } from '../i18n/index.js';
 import { useImagerySplitStore } from './stores/imagerySplit.js';
 import { applicationPinia } from './vueRuntime.js';
 
@@ -16,6 +17,9 @@ function defaultViewportWidth() {
   );
 }
 
+// A title or label given as a function is worded when published.
+const worded = (text) => (typeof text === 'function' ? text() : text);
+
 function defaultValueText(beforePercent, afterPercent) {
   return `A ${beforePercent} percent, B ${afterPercent} percent`;
 }
@@ -30,7 +34,9 @@ function defaultValueText(beforePercent, afterPercent) {
  * `onChange` reports pointer and keyboard changes so the owner can mirror
  * them, and `requestRender` fires whenever the clamped value actually
  * changes. `destroy` is idempotent: it withdraws the line, clears the CSS
- * property and restores the scene split captured at creation once.
+ * property and restores the scene split captured at creation once. The
+ * titles and label may be functions, which are called again after a locale
+ * change, like `formatValueText`.
  */
 export function createImagerySplit({
   scene,
@@ -72,9 +78,9 @@ export function createImagerySplit({
         handleClass: handleClass ?? null,
         beforeLabel,
         afterLabel,
-        beforeTitle: beforeTitle ?? null,
-        afterTitle: afterTitle ?? null,
-        ariaLabel: ariaLabel ?? null,
+        beforeTitle: worded(beforeTitle) ?? null,
+        afterTitle: worded(afterTitle) ?? null,
+        ariaLabel: worded(ariaLabel) ?? null,
         valueNow: beforePercent,
         valueText: formatValueText(beforePercent, 100 - beforePercent),
       },
@@ -144,6 +150,7 @@ export function createImagerySplit({
   };
 
   apply(initialValue, { render: false });
+  const offLocale = onLocaleChange(publish);
 
   return {
     getValue() {
@@ -166,6 +173,7 @@ export function createImagerySplit({
       pointerId = null;
       captor = null;
       destroyed = true;
+      offLocale();
       store.withdraw(key);
       if (cssProperty) cssTarget.style.removeProperty(cssProperty);
       if (scene && restoreValue != null) scene.splitPosition = restoreValue;