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/i18n/locales/ja.json

@@ -9,7 +9,6 @@
   "That line has no length — click somewhere further away.": "線の長さがゼロです。もっと離れた場所をクリックしてください。",
   " · {max}-point limit reached": " · 上限の{max}点に達しました",
   "{measure} · double-click or Enter to finish, Backspace undoes, Esc cancels.{full}": "{measure} · ダブルクリックまたはEnterで完了、Backspaceで元に戻す、Escでキャンセル。{full}",
-  "drawings on the map": "地図上の描画",
   "That shape already has {count} points — finish it or press Backspace.": "この図形はすでに{count}点あります。完了するか、Backspaceを押してください。",
   "That point is off the globe — click on the world.": "その点は地球の外です。地表をクリックしてください。",
   "That shape could not be placed.": "図形を配置できませんでした。",
@@ -394,7 +393,6 @@
   "paste {envVar}": "{envVar}を貼り付け",
   "REMOVE": "削除",
   "Remove {title} from this app's saved keys": "{title}をこのアプリの保存済みキーから削除",
-  "unsaved provider keys": "未保存のプロバイダーキー",
   "Project keys: {status}": "プロジェクトのキー：{status}",
   "your app configuration": "アプリの設定",
   "your local .env": "ローカルの .env",
@@ -1498,9 +1496,6 @@
   "Sensitivity": "感度",
   "WHOT/BHOT": "WHOT/BHOT",
   "Ironbow": "Ironbow",
-  "unsaved CCTV calibration": "未保存のCCTVキャリブレーション",
-  "the open cockpit": "表示中のコックピット",
-  "Switching language reloads the page. This will be lost: {items}. Switch anyway?": "言語を切り替えるとページが再読み込みされます。次の内容は失われます：{items}。切り替えますか？",
   "VISUAL PRESETS": "ビジュアルプリセット",
   "LOCATION": "位置",
   "CONTACTS — nearest planes · vessels · sites": "コンタクト：最寄りの航空機 · 船舶 · 施設",
@@ -1711,7 +1706,6 @@
   "Space Missions": "宇宙ミッション",
   "Context": "コンテキスト",
   "Rendered globe frames per second · toggle with `": "地球儀の描画フレームレート（毎秒） · `キーで切り替え",
-  "imported map files": "インポートした地図ファイル",
   "Ground heights could not be refreshed. Try the file again when the map has loaded.": "地表高を更新できませんでした。地図の読み込み後に、もう一度このファイルをお試しください。",
   "{count} map objects": {
     "other": "地図オブジェクト{count}個"
@@ -2417,7 +2411,6 @@
   "Activate to toggle voice": "押すと音声のオン/オフを切り替え",
   "Voice active": "音声 オン",
   "Voice could not be started.": "音声を開始できませんでした。",
-  "the active voice session": "進行中の音声セッション",
   "{value} feet": "{value}フィート",
   "Fire · FRP {frp} MW": "火災 · FRP {frp} MW",
   "The flights layer is not enabled": "フライトレイヤーが有効になっていません",