A quad counts only when all 8 entries are present, numeric and finite.
Anything else contributes nothing — never folded, shifted or zero-filled
into a box the document does not describe. With no usable quad the
existing /Rect fallback runs, and with neither the mark stays unreadable.
The rule lives in one helper, geom::quad_points::usable_quads, and redact,
render-inspect, annot summaries and annot appearance drawing all read
through it, so the outline shown is the area apply removes. Redact also
follows indirect numbers in /QuadPoints now, which it used to drop.