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/geoFileImport.test.mjs

@@ -9,7 +9,6 @@ import assert from 'node:assert/strict';
 import fs from 'node:fs';
 import { initGeoFileImport, summarize } from './geoFileImport.js';
 import { GeoImportError, MAX_IMPORTED_FILES } from '../data/geoFileImport.js';
-import { describeUnsavedWork } from '../i18n/index.js';
 
 class FakeClassList {
   constructor() {
@@ -149,19 +148,6 @@ const ROW_ACTIONS = {
 };
 const press = (t, row, name) => t.act(ROW_ACTIONS[name], row.id);
 
-// Runs first: tools left by later tests would answer the same registry.
-test('imported files make the language switch ask first', async () => {
-  const t = setup();
-  assert.deepEqual(describeUnsavedWork(), []);
-  await t.tool.importFiles([file('a.geojson')]);
-  assert.deepEqual(describeUnsavedWork(), ['imported map files']);
-  t.tool.remove(t.tool.list()[0].id);
-  assert.deepEqual(describeUnsavedWork(), [], 'nothing left to lose');
-  await t.tool.importFiles([file('b.kml')]);
-  t.tool.destroy();
-  assert.deepEqual(describeUnsavedWork(), [], 'destroy unregisters');
-});
-
 test('returns null without its markup or viewer', () => {
   const document = { getElementById: () => null };
   assert.equal(initGeoFileImport({ viewer: {}, document }), null);