Annotation parsing: /Annots entries resolved into renderable form —
/Rect, /F flags, the /AS-selected normal appearance stream, and the
optional-content membership (/OC). Painting itself happens in
zpdf-content, which replays the appearance stream as a form XObject mapped
onto /Rect (PDF 32000-1 §12.5.5).
Optional-content (layer) configuration: the catalog’s /OCProperties
default configuration determines which optional-content groups render.
Membership evaluation for /OC entries (OCG refs, OCMDs and visibility
expressions) lives in zpdf-content, which has the object graph in hand;
this module only answers “is group X on?”.