Run pcb scan <local.pdf-or-url>. Stdout reports materialized PDF: and
Markdown: paths; read the file at the Markdown: path. Follow its image
links when the task depends on figures, diagrams, or tables.
Prefer source URLs for package metadata. A cached PDF is not a package artifact; do not copy it into the repository by default. If scanning fails, report the failure briefly and use an available PDF-reading fallback.