Interface LocalizedBriefHighlight

One resolved per-language brief highlight.

headline and summary follow the same semantics as extractArtifactHighlight in article-metadata.ts — either may be empty when the localized brief lacks the relevant section.

sourceFile is the run-relative path to the file that produced the highlight; downstream callers can record this when populating manifest.metadataFallback so editors can later audit which locales fell through to English.

sourceLang matches the language code of the brief that produced the highlight (always equal to the requested language for a successful lookup; the caller infers "en" fallback when this module returns null).