The inspector's library facts gain category_scope "image": an image's
own category overrides the inherited one for any link status (linked,
ambiguous, none). Images reads it for output sources only; History reads
it once per inspection inside its snapshot, keyed by the same file key
from the symlink-resolved output folder. A failed read hides the chip
rather than show a possibly wrong value. The chip's hidden prefix names
the origin ("Image category: "); the visible origin text comes in PR 3.