Regira Lang (i18n) (front-end)

@regira/modules/vue/lang — keyed translation dictionaries, {param} interpolation, the useLang composable that holds the active language as reactive state, and a Vue plugin that wires $t / $tm global properties. Entity labels and any user-facing strings are translated through this layer.

What it provides

Export	Purpose
plugin	app.use(plugin, { defaultLang, messages }) — set language + load messages, install $t/$tm.
useLang()	Shared (singleton) i18n state: langCode, messages, translate, setLangCode, loadMessages, …
translate(key, values, langCode, formatArgs?)	Look up a key in a dictionary for a language (falls back to 2-letter prefix).
translateMessage(message, langCode, formatArgs?)	Translate an inline per-language message (or plain string).
formatText(input, formatArgs, options?)	Fill {param} placeholders ({ ignoreCase: true } to match names in any case), or pass a function to transform the string.
ITranslationMessages / ITranslationMessage	The dictionary and per-language message types.
IFormatInput	Interpolation args: a value map or a (input) => string function.
LangSelector	Inline language switcher (langs: string[]) — show it in the header of any multilanguage app.

How it fits

app.use(plugin, { defaultLang, messages })   →  drives the singleton useLang() state
   ├─ $t(key, args?)   in templates          (gated on async messages loading)
   ├─ $tm(message, args?)                     (inline per-language values, e.g. entity fields)
   └─ useLang().translate / setLangCode       (read/switch language anywhere)

defaultLang sets both the active and fallback language. The fallback-language retry lives on useLang().translate (and $t); the bare exported translate only falls back to the 2-letter language prefix (en-US → en).

The same messages translate the validation errors an Entities API sends: a server validator can return a translation key (ValueTooLarge) instead of a full message, and toFeedbackError (from vue/ui, used by every entity form) shows its translation — {param} placeholders filled from the error's args — or the message as sent when the dictionary has no such key. An app that translates with another library, such as vue-i18n, hands toFeedbackError its own translator with setErrorTranslator (from vue/ui).