heading-free documents now window instead of returning whole
- ris_get_document / ris://document/… outlines markdown that overflows the 40,000-byte budget and carries no §/Artikel/Anlage headings into byte windows (Part n of N, document order), retrievable through the existing sections:[…] selector; html and xml stay untouched at any size (#33)
- fix: multi-entry sections:[…] retrieval no longer inserts a blank line between joined entries — the returned text now reassembles the source byte for byte