fix: normalize i18n registry lookup keys

Issue: #62
User-Visible: no

src/i18n/registry.ts

@@ -23,10 +23,6 @@ export type Lang = (typeof LANGUAGE_REGISTRY)[number]['code'];
 export const FALLBACK_LANGUAGE_CODE: Lang = 'en';
 export const FALLBACK_DICTIONARY = en;
 
-const LANGUAGE_BY_CODE = new Map<string, LanguageEntry>(
-  LANGUAGE_REGISTRY.map((entry) => [entry.code, entry]),
-);
-
 /** Normalize HA locale tags for registry lookup. */
 export function normalizeLanguageTag(value: unknown): string {
   return typeof value === 'string'
@@ -34,6 +30,15 @@ export function normalizeLanguageTag(value: unknown): string {
     : '';
 }
 
+/** Build a case-insensitive BCP 47 lookup while retaining canonical codes. */
+export function buildLanguageLookup<T extends { code: string }>(
+  entries: readonly T[],
+): ReadonlyMap<string, T> {
+  return new Map(entries.map((entry) => [normalizeLanguageTag(entry.code), entry]));
+}
+
+const LANGUAGE_BY_CODE = buildLanguageLookup(LANGUAGE_REGISTRY);
+
 /** Return the canonical registry entry for a locale code, if it is shipped. */
 export function languageEntry(value: unknown): LanguageEntry | undefined {
   return LANGUAGE_BY_CODE.get(normalizeLanguageTag(value));