Review found the shared observation defeated the very fence it fed:
it carries the original PID-to-start-time pairing forward, so a
recycled PID still matches it and takes a signal meant for the process
that exited. Capturing it outside the per-member try also let one
failed read abort a whole teardown round, breaking the synchronous
host-exit contract, and an empty round paid a read for no members.
signalProcess now reads ProcessInspector.isAlive immediately before
delivering, from the narrowest per-identity source each platform
offers; signalMembers and waitForMembers return before capturing when
a round has no members. snapshot() keeps serving the readiness poll,
whose per-poll table read stays at one.
Windows enumerates Toolhelp32 lazily on the first tree question, so a
snapshot asked only for liveness — the 25 ms teardown poll — performs
no table walk at all.
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