refactor(i18n): shared define-locale/RTL/endonym scaffolding in @hermes/shared; desktop+web forward to it

Desktop and web each re-implemented the same locale plumbing: the
TranslationOverride<T> partial-catalog type, isRecord (four copies across
the two apps), mergeTranslations, the RTL_LOCALES={'ar'} set with the
documentElement.lang/dir effect, and the endonym table for the language
picker (6 entries on desktop, 17 on web, overlapping and hand-synced).

The generic parts now live once in apps/shared/src/i18n.ts (exported from
the root index and the `@hermes/shared/i18n` subpath). It is generic over
the catalog type — no Translations, no `en` — so translation catalogs stay
per-app (content decision, deliberately not merged here).

Sites (path::symbol → canonical):
  apps/desktop/src/i18n/define-locale.ts::TranslationOverride, isRecord,
      mergeTranslations → @hermes/shared/i18n; defineLocale is a one-liner
  web/src/i18n/define-locale.ts::TranslationOverride, isRecord,
      mergeTranslations → @hermes/shared/i18n; defineLocale is a one-liner
  apps/desktop/src/i18n/runtime.ts::isRecord → shared isRecord
  apps/desktop/src/i18n/context.tsx::isRecord, RTL_LOCALES,
      applyDocumentLocale → shared isRecord / applyDocumentLocale
  web/src/i18n/context.tsx::RTL_LOCALES + inline lang/dir effect
      → shared applyDocumentLocale
  web/src/i18n/context.tsx::LOCALE_META literal (17 names)
      → derived from shared LOCALE_ENDONYMS (same exported shape)
  apps/desktop/src/i18n/languages.ts::LOCALE_OPTIONS.name (6 names)
      → LOCALE_ENDONYMS.<id>; englishName/configValue columns stay

The six desktop endonyms were byte-identical to web's before the move.

Tests: apps/shared/src/i18n.test.ts — mergeTranslations keeps untouched
sibling keys under a nested partial override and replaces functions/arrays
wholesale without mutating the base; RTL_LOCALES ⊆ keys(LOCALE_ENDONYMS);
applyDocumentLocale is a no-op without a document. The existing desktop
context.test.tsx RTL/lang assertions keep covering the effect.

Behavior change: none.

web/src/i18n/context.tsx

@@ -1,3 +1,4 @@
+import { applyDocumentLocale, LOCALE_ENDONYMS } from "@hermes/shared/i18n";
 import { createContext, useContext, useState, useCallback, useEffect, type ReactNode } from "react";
 import type { Locale, Translations } from "./types";
 import { en } from "./en";
@@ -38,40 +39,14 @@ const TRANSLATIONS: Record<Locale, Translations> = {
   ar,
 };
 
-// Locales whose script flows right-to-left. Consumed by the provider to set the
-// document direction so Tailwind's logical utilities (ms-/me-, ps-/pe-) flip.
-const RTL_LOCALES = new Set<Locale>(["ar"]);
-
-// Display metadata for the language picker — endonym (native name) so users
-// recognize their language even if they don't speak the current UI language.
-// Exposed as a constant so the LanguageSwitcher and any future settings page
-// can share the same list.
-//
-// We intentionally do NOT pair locales with country flags. Languages are not
-// countries (English ≠ GB, Portuguese ≠ PT, Spanish ≠ ES, Chinese variants ≠
-// any single jurisdiction). Endonyms are unambiguous and avoid the political
-// mismapping that flag pairings inevitably create.
-export const LOCALE_META: Record<Locale, { name: string }> = {
-  en: { name: "English" },
-  zh: { name: "简体中文" },
-  "zh-hant": { name: "繁體中文" },
-  ja: { name: "日本語" },
-  de: { name: "Deutsch" },
-  es: { name: "Español" },
-  fr: { name: "Français" },
-  tr: { name: "Türkçe" },
-  uk: { name: "Українська" },
-  af: { name: "Afrikaans" },
-  ko: { name: "한국어" },
-  it: { name: "Italiano" },
-  ga: { name: "Gaeilge" },
-  pt: { name: "Português" },
-  ru: { name: "Русский" },
-  hu: { name: "Magyar" },
-  ar: { name: "العربية" },
-};
-
 const SUPPORTED_LOCALES = Object.keys(TRANSLATIONS) as Locale[];
+
+// Display metadata for the language picker — endonyms from @hermes/shared so the
+// desktop and web pickers can never disagree on a language's native name.
+export const LOCALE_META: Record<Locale, { name: string }> = Object.fromEntries(
+  SUPPORTED_LOCALES.map((id) => [id, { name: LOCALE_ENDONYMS[id] }]),
+) as Record<Locale, { name: string }>;
+
 const STORAGE_KEY = "hermes-locale";
 
 function isLocale(value: string): value is Locale {
@@ -113,9 +88,7 @@ export function I18nProvider({ children }: { children: ReactNode }) {
   }, []);
 
   useEffect(() => {
-    if (typeof document === "undefined") return;
-    document.documentElement.lang = locale;
-    document.documentElement.dir = RTL_LOCALES.has(locale) ? "rtl" : "ltr";
+    applyDocumentLocale(locale);
   }, [locale]);
 
   const value: I18nContextValue = {

web/src/i18n/define-locale.ts

@@ -1,46 +1,12 @@
-import { en } from "./en";
-import type { Translations } from "./types";
+import { mergeTranslations, type TranslationOverride } from '@hermes/shared/i18n'
+
+import { en } from './en'
+import type { Translations } from './types'
 
 // Partial-locale helper: a translation file supplies only the strings it has
 // translated and every missing key falls back to English, while unknown keys
-// still fail the type-check. Mirrors the desktop app's `defineLocale` so a new
-// locale (e.g. Arabic) can land without hand-porting every future English key.
+// still fail the type-check.
+export type TranslationOverrides = TranslationOverride<Translations>
 
-type TranslationOverride<T> = T extends (...args: never[]) => string
-  ? T
-  : T extends readonly unknown[]
-    ? T
-    : T extends string
-      ? string
-      : T extends object
-        ? { [K in keyof T]?: TranslationOverride<T[K]> }
-        : T;
-
-export type TranslationOverrides = TranslationOverride<Translations>;
-
-function isRecord(value: unknown): value is Record<string, unknown> {
-  return typeof value === "object" && value !== null && !Array.isArray(value);
-}
-
-function mergeTranslations<T>(base: T, overrides: TranslationOverride<T> | undefined): T {
-  if (!isRecord(base) || !isRecord(overrides)) {
-    return (overrides ?? base) as T;
-  }
-
-  const result: Record<string, unknown> = { ...base };
-
-  for (const [key, value] of Object.entries(overrides)) {
-    if (value === undefined) {
-      continue;
-    }
-
-    const baseValue = result[key];
-    result[key] = isRecord(baseValue) && isRecord(value) ? mergeTranslations(baseValue, value) : value;
-  }
-
-  return result as T;
-}
-
-export function defineLocale(overrides: TranslationOverrides): Translations {
-  return mergeTranslations<Translations>(en, overrides);
-}
+export const defineLocale = (overrides: TranslationOverrides): Translations =>
+  mergeTranslations<Translations>(en, overrides)

web/tsconfig.app.json

@@ -19,7 +19,9 @@
     /* Path aliases */
     "paths": {
       "@/*": ["./src/*"],
-      "@hermes/shared": ["../apps/shared/src/index.ts"]
+      "@hermes/shared": ["../apps/shared/src/index.ts"],
+      "@hermes/shared/ansi": ["../apps/shared/src/ansi.ts"],
+      "@hermes/shared/i18n": ["../apps/shared/src/i18n.ts"]
     },
 
     /* Linting */