Function worker_extraction_version 

pub async fn worker_extraction_version(
    bin: &Path,
    timeout: Duration,
) -> Option<u32>

Ask the worker binary at bin which extraction format it produces, giving up after timeout.

The worker is a separately installed binary, so a caller’s own EXTRACTION_VERSION says nothing about what actually parses: a new CLI driving an old worker emits pre-upgrade extraction while believing it emitted current data (#228). This is how the caller finds out instead of assuming.

None means unknown, never agreed. It covers every way the answer can fail to arrive — the binary is missing or not executable, it exits non-zero, it prints something unparseable, it hangs, or it is a pre-#228 worker that ignores argv and blocks on stdin (the probe closes stdin, so such a worker exits silently). A caller must treat None as a version that cannot match.