#4195 fixed `d /run/hyperhive` to 0751, matching hive-c0re.service's own
RuntimeDirectoryMode and docs/trust-boundary/boundary.md. Nothing stops
it drifting back: the mode is a string literal inside a function that
writes a file and then shells out to systemd-tmpfiles, and a test can do
neither of those things.
`agent_tmpfiles_content` splits the pure content builder out so the modes
can be asserted at all. Two tests:
- /run/hyperhive is 0751, and explicitly NOT 0750 — the regression #4195
fixed. 0750 denies the `o=--x` traversal a `hive-admin` member who is
not in `hive-core` needs to reach host.sock, before the socket's own
0660 gate is ever consulted.
- the per-agent socket dir line, and that the body grows with the roster.
A mode nobody can assert is a mode that drifts. This adds no behaviour
change of its own; it pins the one #4195 landed.
Refs #4195.
6e190eeef1