Covers proposed rules, notices, AND final/interim rules that accept
comments (dozens of RULE-type documents have open periods at any time).
Queries for comment close date >= today, scans up to 500 matching
documents oldest-published first (where the soonest deadlines live),
sorts by close date, and returns the first `limit`.

Source scope: total_open is the API's matching metadata count;
scanned is how many this call examined. When total_open exceeds
scanned, narrow with agencies/term for complete indexed coverage. A very
recently published document with an unusually short comment window
can fall outside the scan in that oversubscribed case.

complete means the matching indexed records were scanned, not that every
currently open opportunity or controlling deadline was verified. The API's
comments_close_on metadata can disagree with DATES after an extension or
reopening. Even a zero result needs docket/subject search_documents and
get_document DATES/linked publication checks before ruling out comments.

Default: searches all agencies. Pass agency slugs to narrow scope,
e.g. ['defense-acquisition-regulations-system'] for DFARS or
['general-services-administration'] for GSA and GSAR.

Parameters:
- far_council: True for open FAR proposed rules and FAR information
  collections (documents filed jointly by DoD, GSA and NASA; there is no
  single FAR agency slug and the OFPP tag only appears from about
  mid-2025). Cannot be combined with agencies.
- limit: max documents returned after sorting (default 50, max 100).
  Unfiltered dumps across all agencies can approach 200KB; several
  broad agencies together (e.g. DoD + GSA) can pass 100KB, so lower
  limit for those.