/**
 * Reduces a transcript to the one line a verdict's detail slot carries, or `undefined` when it held nothing.
 *
 * The excerpt is the last blank-line-delimited block: a tool that prints progress separates its closing
 * statement with a blank line, so the blank line is the tool naming where its summary starts. A fixed count of
 * trailing lines fits vitest's four-line summary and v8's six-line coverage summary only by coincidence.
 *
 * The line carries a byte bound of its own, so what a caller persists is bounded. The 512-byte ceiling a
 * verdict line is held to is not applied here, which leaves that line's grammar with the module that owns it.
 */
export declare function deriveExcerpt(transcript: string): string | undefined;