feat: report per-node validation detail

[dholt]

Add per-node detail to DeepOps validators

What this is

Implement the 26.09 public validator improvement: add stable per-node detail to the --json output of validate_slurm.py and validate_k8s.py while preserving existing aggregate fields and exit behavior. Slurm detail must report each unique node's normalized state and configured GRES GPU count. Kubernetes detail must report each node's Ready status and allocatable nvidia.com/gpu count, handling malformed values as zero. Add focused stdlib unit tests, update the validator skill only where needed, and keep human output compatible. Do not access a live scheduler or cluster; use parser fixtures only. Do not push or open a PR.

Verification

• Deterministic checks passed: diff check, validation tests, python compile, public sanitizer, parent commit
• Two independent agent reviews approved head abf0007eb062 (different model vendors; strict verdict contract)
• Published by the DeepOps maintenance loop's deterministic publisher after its publication gate (reviews, provenance, exact-head) passed