Add links to Rust nightly documentation for installation prerequisites to help users understand how to install and configure the nightly toolchain.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

when a job is not yet in running state the program runs but the function
that lists the job's machines returns zero machines which can cause a
panic from division by 0 which is not a very helpful message. this
commit improves the error/warn messages when no machines are listed for
a job.

if we are unable to obtain the hostname of the local machine from the
/etc/hostname file or HOSTNAME env var then an empty string is used as
the hostname and a warning is shown instead of a panic. since the
hostname is just used to determine if we are executing on the cluster,
and the cluster machines all have their hostnames set, then using the
empty string should not be a problem.

some docker networks and the swarm can create routing rules that
conflict with the ones we create leading to errors such as:

59:2025-10-15T15:07:33.745853Z  WARN Failed to connect to 10.0.1.243:4000: No route to host (os error 113)
89:2025-10-15T15:08:30.197646Z  WARN Failed to connect to 10.0.1.32:4000: No route to host (os error 113)
92:2025-10-15T15:08:30.837360Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
95:2025-10-15T15:08:33.905356Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
98:2025-10-15T15:08:36.981419Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
101:2025-10-15T15:08:40.049335Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
104:2025-10-15T15:08:43.121680Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
107:2025-10-15T15:08:46.197394Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
110:2025-10-15T15:08:49.265514Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
113:2025-10-15T15:08:52.337454Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
116:2025-10-15T15:08:55.409444Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
119:2025-10-15T15:08:58.481471Z  WARN Failed to connect to 10.0.1.91:4000: No route to host (os error 113)
1