Two compounding bugs on a title/back-page background image:
- its host paragraph picks up position:relative from the line-height
rule, becoming the frame's containing block instead of the page and
offsetting it by a full page margin — now forced back to static.
- the frame always painted behind text (z-index -1); a graphic that
declares ODF's style:run-through="foreground" now paints in front,
as LibreOffice draws it, via a new inFront attr round-tripped through
ODF export/import.
Confirmed against LibreOffice's own render: the duplicated, ~2cm
displaced cover graphic now matches exactly.