[Issue]: scontrol show hostnames/hostlist/hostnamestr is missing

[SumonAMD]

Problem Description

Spur's scontrol does not implement show hostnames [NODELIST] or the hostlist / hostnamestr variants that Slurm provides.

Why it matters: these are the idiomatic way distributed jobs discover their nodes. A very common line in launch scripts is:

MASTER_ADDR=$(scontrol show hostnames "$SLURM_JOB_NODELIST" | head -n1)

Without these subcommands, Slurm rendezvous scripts (torchrun and similar) don't work unchanged on spur.

Expected:

• hostnames — expand a hostlist to one hostname per line
• hostlist — collapse hostnames into a compact bracketed expression
• hostnamestr — expand to a single comma-separated line

They should work outside an allocation and while the controller is down, and fall
back to $SLURM_JOB_NODELIST / $SLURM_NODELIST when no argument is given, as
Slurm does.

Environment

• OS: Ubuntu 22.04 LTS
• CPU: AMD EPYC (x86_64 server-class)
• GPU: AMD Instinct MI300X
• ROCm Version: N/A — feature gap in the spur CLI, independent of the ROCm runtime
• Component: spur

Steps to Reproduce

scontrol show hostnames node[1-4]     # not implemented
scontrol show hostlist node1,node2    # not implemented
scontrol show hostnamestr node[1-4]   # not implemented