The container entrypoint ran `chown -R` on $HERMES_HOME every start.
`chown` strips the setgid bit (kernel security behavior), destroying
the 2770 permissions the NixOS activation script sets for group access
by hostUsers. This caused PermissionError for interactive CLI users
even though they were in the hermes group.
Replace with `find ... ! -user $UID -exec chown` which only touches
files with wrong ownership, leaving correctly-owned directories and
their permission bits intact.
Affects: container.enable + container.hostUsers + addToSystemPackages
Related: #19795, #19788, #9383
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