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.
MacProcessInspector answered the descendant tree and every member's
liveness with its own `/bin/ps` fork, so one readiness poll cost N+1
full table reads for N tracked descendants. With execFileSync on that
path and a 50 ms poll interval, any command spawning two or more
children saturated the host event loop until it exited.
ProcessInspector.snapshot() now returns one ProcessSnapshot that
answers tree, session, and alive from a single observation, and
signalProcess takes the caller's observation so its PID-reuse fence
does not re-read the table per member.
Yichen Jiang