docker run/exec argv previously carried -e KEY=VALUE pairs for every
forwarded/passthrough variable. On Linux /proc/<pid>/cmdline is
world-readable regardless of process owner, so every allowlisted secret
was visible to all local users via plain ps for the duration of every
terminal call.
Emit name-only -e KEY flags and supply values via the docker client
subprocess env instead: the docker CLI resolves valueless --env KEY from
its own environment (documented docker/podman behavior), moving secrets
from /proc/*/cmdline (0444) to /proc/*/environ (0400). Covers the docker
run container-start path, the recreation/recovery path, the init-seeding
exec path, and the per-command runtime exec path.
Reported by @sashalab. Fixes#96268
d10ef89ee5