Settings: language and theme, kept in the app

Appearance in Settings chooses the language (the system's, or one of the nine the app has;
the window opens again in it, its replies and shells let go first) and the theme (the
account's, or Moria or Shire, drawn at once and the window painted in it). Kept in
localStorage on this computer: /api/v2 has no PATCH /me for either yet, so the account's
own stay as they are. i18n.js reads the choice and carries each language's own name from
the server's catalogue. Tests E5.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

scripts/gen-i18n.py

@@ -458,6 +458,17 @@ KEYS = (
     "Type a folder…",
     "Choose a folder first.",
     "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.",
+    # settings.js: language and theme
+    "Appearance",
+    "Language",
+    "Theme",
+    "dark",
+    "light",
+    "The interface only. Models answer in the language you write to them in, whatever this says.",
+    "This computer's (%(language)s)",
+    "The account's (%(theme)s)",
+    "Kept in this app on this computer. The window opens again in the language chosen.",
+    "Kept in this app on this computer; the account's theme stays as it is.",
 )
 
 # The app's own sentences. The mode names (Manual, Edit, Auto, Plan) stay English, as the
@@ -695,6 +706,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Zadat složku…",
         "Choose a folder first.": "Nejprve vyberte složku.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Agentní konverzace pracuje ve složce na zařízení %(device)s přes tamního agenta LLeMbas.",
+        "This computer's (%(language)s)": "Podle tohoto počítače (%(language)s)",
+        "The account's (%(theme)s)": "Podle účtu (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Uloženo v této aplikaci na tomto počítači. Okno se znovu otevře ve zvoleném jazyce.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Uloženo v této aplikaci na tomto počítači; vzhled účtu zůstává, jak je.",
     },
     "de": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Melden Sie sich erneut an: Der Server nimmt die Anmeldung dieser App nicht mehr an.",
@@ -927,6 +942,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Ordner eingeben…",
         "Choose a folder first.": "Wählen Sie zuerst einen Ordner.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Ein Agenten-Chat arbeitet in einem Ordner auf %(device)s, über den LLeMbas-Agenten dort.",
+        "This computer's (%(language)s)": "Wie dieser Computer (%(language)s)",
+        "The account's (%(theme)s)": "Wie das Konto (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "In dieser App auf diesem Computer gespeichert. Das Fenster öffnet sich in der gewählten Sprache neu.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "In dieser App auf diesem Computer gespeichert; das Design des Kontos bleibt, wie es ist.",
     },
     "es": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Vuelva a iniciar sesión: el servidor ya no acepta el inicio de sesión de esta aplicación.",
@@ -1159,6 +1178,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Escribir una carpeta…",
         "Choose a folder first.": "Elija primero una carpeta.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Un chat de agente trabaja en una carpeta de %(device)s, a través del agente LLeMbas de allí.",
+        "This computer's (%(language)s)": "La de este equipo (%(language)s)",
+        "The account's (%(theme)s)": "El de la cuenta (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Se guarda en esta aplicación en este equipo. La ventana se vuelve a abrir en el idioma elegido.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Se guarda en esta aplicación en este equipo; el tema de la cuenta no cambia.",
     },
     "fr": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Reconnectez-vous : le serveur n’accepte plus la connexion de cette application.",
@@ -1391,6 +1414,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Saisir un dossier…",
         "Choose a folder first.": "Choisissez d’abord un dossier.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Une discussion d'agent travaille dans un dossier de %(device)s, via l'agent LLeMbas qui s'y trouve.",
+        "This computer's (%(language)s)": "Celle de cet ordinateur (%(language)s)",
+        "The account's (%(theme)s)": "Celui du compte (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Enregistré dans cette application sur cet ordinateur. La fenêtre se rouvre dans la langue choisie.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Enregistré dans cette application sur cet ordinateur ; le thème du compte reste tel quel.",
     },
     "hu": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Jelentkezzen be újra: a szerver már nem fogadja el ennek az alkalmazásnak a bejelentkezését.",
@@ -1623,6 +1650,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Mappa megadása…",
         "Choose a folder first.": "Először válasszon mappát.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Az ügynökcsevegés egy mappában dolgozik ezen: %(device)s, az ottani LLeMbas-ügynökön keresztül.",
+        "This computer's (%(language)s)": "A számítógépé (%(language)s)",
+        "The account's (%(theme)s)": "A fióké (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Ebben az alkalmazásban, ezen a számítógépen tárolva. Az ablak a választott nyelven nyílik meg újra.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Ebben az alkalmazásban, ezen a számítógépen tárolva; a fiók témája változatlan marad.",
     },
     "it": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Accedi di nuovo: il server non accetta più l’accesso di questa app.",
@@ -1855,6 +1886,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Digita una cartella…",
         "Choose a folder first.": "Scegli prima una cartella.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Una chat con agente lavora in una cartella su %(device)s, tramite l’agente LLeMbas che vi si trova.",
+        "This computer's (%(language)s)": "Quella di questo computer (%(language)s)",
+        "The account's (%(theme)s)": "Quello dell’account (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Salvato in questa app su questo computer. La finestra si riapre nella lingua scelta.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Salvato in questa app su questo computer; il tema dell’account resta com’è.",
     },
     "pl": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Zaloguj się ponownie: serwer nie przyjmuje już logowania tej aplikacji.",
@@ -2087,6 +2122,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Wpisz folder…",
         "Choose a folder first.": "Najpierw wybierz folder.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Czat z agentem pracuje w folderze na %(device)s, przez działającego tam agenta LLeMbas.",
+        "This computer's (%(language)s)": "Jak na tym komputerze (%(language)s)",
+        "The account's (%(theme)s)": "Jak na koncie (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Zapisane w tej aplikacji na tym komputerze. Okno otworzy się ponownie w wybranym języku.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Zapisane w tej aplikacji na tym komputerze; motyw konta pozostaje bez zmian.",
     },
     "sk": {
         "Sign in again: the server no longer accepts this app's sign-in.": "Prihláste sa znova: server už neprijíma prihlásenie tejto aplikácie.",
@@ -2319,6 +2358,10 @@ OWN: dict[str, dict[str, str]] = {
         "Type a folder…": "Zadať priečinok…",
         "Choose a folder first.": "Najprv vyberte priečinok.",
         "An agent chat works in a folder on %(device)s, through the LLeMbas agent there.": "Agentská konverzácia pracuje v priečinku na zariadení %(device)s cez tamojšieho agenta LLeMbas.",
+        "This computer's (%(language)s)": "Podľa tohto počítača (%(language)s)",
+        "The account's (%(theme)s)": "Podľa účtu (%(theme)s)",
+        "Kept in this app on this computer. The window opens again in the language chosen.": "Uložené v tejto aplikácii na tomto počítači. Okno sa znova otvorí vo zvolenom jazyku.",
+        "Kept in this app on this computer; the account's theme stays as it is.": "Uložené v tejto aplikácii na tomto počítači; vzhľad účtu zostáva, ako je.",
     },
 }
 
@@ -2337,9 +2380,13 @@ def server_catalogue(server: Path, lang: str) -> dict[str, str]:
     messages = getattr(module, "MESSAGES", None)
     if not isinstance(messages, dict):
         sys.exit(f"gen-i18n: {path} has no MESSAGES")
+    NAMES[lang] = str(getattr(module, "NAME", "") or lang)
     return messages
 
 
+NAMES: dict[str, str] = {}  # each language's own name for itself, as the server's catalogue says
+
+
 def main() -> None:
     server = Path(sys.argv[1] if len(sys.argv) > 1 else os.environ.get("LEMBAS_SERVER", ROOT.parent / "LLeMbas"))
     catalogue: dict[str, dict[str, str]] = {}
@@ -2372,24 +2419,38 @@ def main() -> None:
         print(f"gen-i18n: {lang}: {len(table)} sentences, {from_server} of the page's {len(KEYS)} from the server")
 
     body = json.dumps(catalogue, ensure_ascii=False, indent=2, sort_keys=True)
+    names = json.dumps({"en": "English", **NAMES}, ensure_ascii=False, sort_keys=True)
     out = (
         "// The app's own pages' words in the server's languages. GENERATED by scripts/gen-i18n.py:\n"
         "// the sentences the server also has come from its web/i18n catalogues, the rest from the\n"
         "// script's own table. Do not edit; run the script.\n"
         "//\n"
         "// `t(text, fields)` is the page's English with `%(name)s` fields, as on the server; a\n"
-        "// missing entry is the English. The language is the system's (navigator.language),\n"
-        "// English unless it is one of these. Elements marked `data-i18n` (their text) and\n"
+        "// missing entry is the English. The language is the one chosen in Settings (kept in\n"
+        "// localStorage as `lembas.language`), else the system's (navigator.language), English\n"
+        "// unless it is one of these. Elements marked `data-i18n` (their text) and\n"
         "// `data-i18n-title`, `data-i18n-aria-label`, `data-i18n-placeholder` (that attribute)\n"
         "// are translated once the page is parsed; this script is deferred, before the page's.\n"
         '"use strict"\n'
         "\n"
         f"const LEMBAS_I18N = {body}\n"
         "\n"
-        "const LEMBAS_LANG = (() => {\n"
+        "// Each language's name for itself, for the choice in Settings.\n"
+        f"const LEMBAS_LANGS = {names}\n"
+        "\n"
+        "// What the system's language gives, and what was chosen here instead (\"\" for the system's).\n"
+        "const LEMBAS_SYSTEM_LANG = (() => {\n"
         '  const code = String(navigator.language || "").slice(0, 2).toLowerCase()\n'
         '  return Object.prototype.hasOwnProperty.call(LEMBAS_I18N, code) ? code : "en"\n'
         "})()\n"
+        "const LEMBAS_CHOSEN_LANG = (() => {\n"
+        '  let code = ""\n'
+        "  try {\n"
+        '    code = localStorage.getItem("lembas.language") || ""\n'
+        "  } catch {}\n"
+        '  return Object.prototype.hasOwnProperty.call(LEMBAS_LANGS, code) ? code : ""\n'
+        "})()\n"
+        "const LEMBAS_LANG = LEMBAS_CHOSEN_LANG || LEMBAS_SYSTEM_LANG\n"
         "document.documentElement.lang = LEMBAS_LANG\n"
         "\n"
         "function t(text, fields) {\n"