reapOrphans() treats any recorded backend with a matching process identity
as orphan-reapable — including a backend owned by another live instance. The
ownership file is shared across instances, so a second launch that reaches
reap (even without the lock) SIGTERMs the running instance's backend.
Claims now record the spawning Electron (parentPid + parentStartMarker, the
same values already passed to the backend as HERMES_PARENT_PID /
HERMES_PARENT_START_MARKER), and reapOrphans() skips any entry whose parent
is still running. Even a second instance that wins a stale lock can never
kill a live instance's backend. Legacy entries without parent data keep the
old behaviour.
Known tradeoff: a parent-liveness probe failure preserves the record, so a
genuinely orphaned backend under a still-running parent is leaked until it
dies naturally. That is preferable to killing a live instance's backend.
Tests: parent-aware reap in backend-ownership.test.ts (live parent
preserved, dead parent still reaped, probe failure preserved, parent
identity round-trips through claim/parse).
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