Architecture review fixes: partials carry the locale, mountable locales/, shared core words

src/i18n/english.ts

@@ -3,13 +3,20 @@
 // view model built outside a request, an app created without `i18n` — so an unwired path renders
 // real English rather than bare keys. server.ts replaces it with the discovered catalogs at boot.
 
-import { DEFAULT_LOCALE } from "./catalog.ts";
+import { type Catalog, DEFAULT_LOCALE } from "./catalog.ts";
 import enUS from "./locales/en-US.ts";
 import { createI18n, type I18n } from "./runtime.ts";
 import { createTranslator, type Translate } from "./translate.ts";
 
 export const ENGLISH: Translate = createTranslator({ catalogs: [enUS], locale: DEFAULT_LOCALE });
 
+// A plugin's own English: its catalog first, the host's behind it — the same chain the host builds
+// per request, minus the locale. A plugin uses it as the default for a view model built outside a
+// request (its unit tests), so the generic words it reuses from core still read as words.
+export function englishTranslator(catalog: Catalog): Translate {
+  return createTranslator({ catalogs: [catalog, enUS], locale: DEFAULT_LOCALE });
+}
+
 export const ENGLISH_I18N: I18n = createI18n({
   available: [DEFAULT_LOCALE],
   core: new Map([[DEFAULT_LOCALE, enUS]]),