_split_oversized slices at fixed char offsets and can cut a
\x00KB_PAGE:N\x00 sentinel in half — the broken prefix/suffix no longer
matches _PAGE_MARKER_RE so _strip_page_markers leaves the \x00 byte in
place. PostgreSQL's UTF-8 check then rejects the insert with
"invalid byte sequence for encoding UTF8: 0x00", and ingest of
ספר הליקויים fails on every scan. Belt-and-suspenders: strip all
remaining \x00 bytes from clean content before returning.
Refs Task Master #2
chaim
1ca1cc0050