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/keySetup.test.mjs

@@ -8,7 +8,6 @@ import {
   initKeySetup,
 } from './keySetup.js';
 import { createPinia } from 'pinia';
-import { describeUnsavedWork } from './i18n/index.js';
 import { useProviderSettingsStore } from './ui/stores/providerSettings.js';
 
 const freshStore = () => useProviderSettingsStore(createPinia());
@@ -129,31 +128,3 @@ test('aborting pending setup removes its surface and ignores a late response', a
   assert.equal(await pending, null);
   assert.equal(store.view.available, false);
 });
-
-test('a pasted, unsaved key makes the language switch ask first until teardown', async () => {
-  const store = freshStore();
-  const root = { dataset: {} };
-  const controller = new AbortController();
-  const setup = await initKeySetup({
-    documentRef: {
-      getElementById: (id) => (id === 'key-setup' ? root : null),
-      addEventListener() {},
-      removeEventListener() {},
-    },
-    signal: controller.signal,
-    store,
-    fetchImpl: async () => ({
-      ok: true,
-      json: async () => ({ keys: [], setCount: 0, total: 1 }),
-    }),
-  });
-  assert.ok(setup);
-  assert.deepEqual(describeUnsavedWork(), []);
-  store.controls.setField('GOOGLE_MAPS_API_KEY', '   ');
-  assert.deepEqual(describeUnsavedWork(), []);
-  store.controls.setField('GOOGLE_MAPS_API_KEY', 'AIza-pasted');
-  assert.deepEqual(describeUnsavedWork(), ['unsaved provider keys']);
-  // The field still holds the key, so only teardown dropping the check clears it.
-  controller.abort();
-  assert.deepEqual(describeUnsavedWork(), []);
-});