Use the SARIF skill at sarif-parsing/SKILL.md to read scan.sarif and return
its total finding count and by_level counts. The skill's {baseDir} denotes the
sarif-parsing directory. You may inspect its supporting files or execute its
standard-library helper read-only. Do not run a new scanner, change files, use
network services, or delegate. Return only the requested JSON. Empty severity
categories should be omitted. This is a real maintainer lint report; do not
invent findings or infer skill routing success from this explicit invocation.