Implementation of the localize_resolve_locale tool.

Given a caller-supplied locale (atom or string), show every stage Localize takes to canonicalise it — parse → canonicalise → validate → resolve cldr_locale_id → walk the parent chain → membership in :supported_locales. Designed to answer the family of questions "is :en_au the right form?" / "does my locale fall back to en or und?" / "is this in my :supported_locales list?" in a single tool call.