Parameters:
    - filters (optional): every field optional, AND-combined. Shared core (both
      countries): name (substring), query (MEANING-based hybrid search over the
      registered purpose - both countries), status (active|inactive|all, default all),
      legal_form, bundesland, city, postal_code (prefix; AT PLZ 4-digit, DE 5-digit),
      near {place | postal_code, radius_km} (radius search, matches from EVERY queried
      country within the radius - works across the border), nace_section (A-U; OENACE
      == WZ == NACE Rev. 2, so one industry code filters both countries), gegenstand
      (literal substring over the registered activity text), manager_name (person
      search), company_ids (prefixed watchlist, e.g. ["AT:123456a",
      "DE:D2601_HRB135076"], max 100), nace_division/group/class, founded_year_min/max,
      and the balance-sheet screens size_gkl (AT W/K/M/G or DE kleinst/klein/mittel/
      gross, translated per register), bilanzsumme_min/max, equity_ratio_min/max
      (fraction, 0.35 = 35 %), has_guv, growth_profile - in Germany these match only
      companies with a parsed Jahresabschluss (rollout per Bundesland, see
      get_coverage; a notice states the scope). AT-only today (see describe_fields
      capabilities): revenue/employees ranges, has_guv_latest, last_filing_year_min,
      gf_age_min, event_signal/since/until. DE-only: registergericht, capital_min/max
      (Stammkapital). Country aliases (geschaeftszweig, oenace_*, wz_section, fnrs,
      stammkapital_*) are accepted.
    - sort (optional): {field, descending}. AT fields: bilanzsumme (default), revenue,
      equity_ratio, employees, last_filing_year, revenue_growth_1y/3y/5y, distance.
      DE fields: name, register_nummer, capital, bilanzsumme, equity_ratio, revenue
      (financial sorts rank the companies with figures first). A country that cannot
      sort by the requested field returns its default order (reported in notices).
    - page (default 1), page_size (default 25).
    - after (optional): KEYSET paging for bulk extraction - single country only
      (cursors are per register). Pass "" to start, then the country's next_after
      from per_country.
    - exact_count (optional, default false): force exact totals (costs a full scan).
    - country (optional, default "all"): "AT" | "DE" | "all".

    Returns {countries, total: {AT, DE, combined}, results, per_country, notices}.
    ``results`` are compact cards, each with ``country`` and the prefixed
    ``company_id``; with country="all" the list is AT block then DE block - each
    country keeps its own ranking (no fake interleave). ``per_country`` carries each
    register's own envelope (exact totals or lower bounds, applied_filters,
    relaxations on zero hits, query_mode, next_after). A filter one country does not
    support excludes that country and says so in ``notices`` - it is never silently
    dropped; an unreachable backend appears in ``countries_unavailable`` instead of
    failing the call. Never report a German company's financials as zero - the German
    Jahresabschluss rollout is per Bundesland, so a company without figures has not
    been processed yet or files none (see get_coverage and
    financials.reporting_status in get_company_details).

    For one company's full profile use get_company_details; for a downloadable list
    use export_companies_csv; for dataset completeness use get_coverage.