Moving agents.conf/gateway.htpasswd out of StateDirectory (0e1a975f)
left hive-c0re unable to write them at all: ProtectSystem=strict only
keeps StateDirectory and RuntimeDirectory writable, so every write to
/var/lib/hive-gateway/conf failed with EROFS. agents.conf never got
past the tmpfiles pre-seed, so nginx had no location block for any
agent.