Checksum and SSHSIG verification prove the downloaded artifact matches
what was published, not that it can run on this host or is the version
the user approved. The apply pipeline previously swapped the binary and
exited, relying on systemd to restart into an unproven executable; a
wrong-arch fallback asset or unstamped build would take Pulse down with
the backup left unused.
ApplyUpdate now locates the extracted binary and probes it with
--version before the backup and swap stages, failing the update with
zero changes applied when the probe fails or reports a version other
than the apply target. Same pattern the agent updater already uses.
Pinned in the deployment-installability contract with
internal/updates/selftest_test.go as the owned proof surface.
rcourtman