Under a category the link read keeps only links whose raw recipe or
positive category is the value (Python still decides the inherited
one), the links of images whose own category is the value are read by
path, and plain reads skip the inherited-category work. The own-category
map is keyed by normalized path. TESTING.md records D141, D142 and D145
and amends D13, D36 and D39; the filter budget seeds 2,000 own
categories.