Per-annotation percentage derivation (deriveAnnotationPercentage) built a
fresh CFIConverter for every highlight/note/bookmark, re-reading and
re-parsing the whole EPUB each time. Export SectionPercentageCached so
handlers reach the same bounded cache ConvertToCanonical already uses
(8 books, insertion-order eviction): one parse per book per push instead
of one per annotation.
john-okeefe
5a6c361c11