List filers with identity and row coverage.

The filer directory behind every disclosure row. member_id is a Veridion slug and is stable for a single tenure; person_id is the official Bioguide identifier and spans linked tenures, so it is the correct key for joining a person across chambers or non-consecutive service. Row counts are per filer and are drawn from the same served corpus as /api/v1/disclosures, so a member total here reconciles with a filtered query there. Supports conditional requests and returns 304 when the directory is unchanged. Both envelopes include paper_transcriptions.by_member independently of directory rows: pending-only filers remain visible without changing count, coverage or cursor semantics. Exact member_id filters also match paper metadata. State/Bioguide filters require matching directory identities in the returned page and explicitly disclose that limitation. Existing rows include their paper block; unknown paper counts remain null. Measurement-clock changes alone do not change the weak validator, but queue evidence changes do.