The sync probe added for the pre-commit re-check duplicates the Effect
one's rules by hand — positive pid, live process, unparseable means no.
Two implementations of one rule drift apart silently, and this branch has
already produced several bugs of exactly that shape.

Asserts every case against both probes rather than trusting them to
agree: live in either state dir, dead pid, pid 0 and -1, malformed JSON,
and JSON with no pid. Confirmed the parity test fails when the sync
probe's positive-pid guard is removed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>