X_IMAGE_CONTENT_UNIGNORED
Means
a *.dockerignore in this tree does not exclude **/*.test.ts, **/*.test.tsx or the anchored docs, or a later ! line undoes one
Typical cause
the build stage's COPY . . then carries files no boot reads, and an edit to one reruns every line below it, x build --target prebuilt included. A !docs/<path> for one file is the documented escape and no finding
Fix
bun run scripts/image-contract.ts --json: its fix appends the missing lines to the file it names