Each of these wrote its file in place (or set the mode after the
write), so a write cut short by a kill or a full disk left a partial
file behind, and some secrets existed for a moment at umask mode:
- swarm-authelia/swarm-grafana/hive-forge/swarm-bao generators: a
partial file passed the `-s`/`-e` guard and was kept forever. They now
capture the value first and land it with `atomic_write_secret`.
- swarm-controller webhook secret: a truncated file failed the 64-hex
check and the secret was regenerated, out of step with the forge
hooks. It is now written 0600 to a sibling temp, fsynced, renamed.
- hive-c0re htpasswd: the temp is now fsynced and set 0644 before the
rename, like the sibling agents.conf writer, instead of relying on
c0re's umask.
- hivectl wg init: the private key is created 0400 in a temp and
renamed, instead of written at umask mode and chmod'ed after.
Closes#5068
01b8387ab8