eval skill: auto-detect predefined per-cluster execution configs (#1599)

### What does this PR do?

Type of change: documentation

Some NEL installs ship ready-made per-cluster execution configs as an
`internal/slurm/<cluster>` group (via the optional
`nemo_evaluator_launcher_internal` package). When present, the matching
one pre-fills the cluster's `hostname` / `partition` / `gres` (and
node-exclusivity), so the user only sets `account` / `output_dir` /
`walltime` instead of hand-entering the hostname.

- **`SKILL.md` Step 4** — adds a "check FIRST" step: run a discovery
snippet that lists the available `cluster → hostname` pairs **from the
installed package at runtime**; on a hostname match, use `defaults: -
execution: internal/slurm/<cluster>` (replacing `slurm/default`) and
drop the now-redundant `execution.hostname`. If the package isn't
installed or nothing matches, fall back to `slurm/default` and fill the
fields manually.
- **`example_eval.yaml`** — a short, name-free comment on the `defaults`
block pointing to that check.

**Discovery-based by design (no internal data committed):** cluster
names, hostnames, and accounts are read from the install at runtime and
are **not** hardcoded here. The only internal references in the repo are
the package name `nemo_evaluator_launcher_internal` and the generic
`internal/slurm/<cluster>` group pattern. External users without the
package degrade gracefully (import fails → `slurm/default`).

### Usage

N/A — documentation / skill guidance only.

### Testing

Ran the discovery snippet verbatim (lists `cluster → hostname` from the
installed package) and confirmed `internal/slurm/<cluster>` resolves via
a `--dry-run`. `pre-commit run` passes (markdownlint + YAML format).
Grep-verified no cluster names/hostnames are hardcoded in the changed
files.

### Before your PR is "*Ready for review*"

- Is this change backward compatible?: ✅ (falls back to `slurm/default`)
- If you copied code from any other sources or added a new PIP
dependency, did you follow guidance in `CONTRIBUTING.md`: N/A
- Did you write any new necessary tests?: N/A (documentation)
- Did you update Changelog?: N/A (skill docs)
- Did you get Claude approval on this PR?: ❌ (pending)

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

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **Documentation**
* Added Step 4 guidance for discovering and using optional internal
per-cluster SLURM execution configs: how to list available internal
configs, select the matching cluster by switching the default execution,
remove redundant hostname entries, and verify with a --dry-run.
* Clarified that slurm/default is cluster-agnostic, recommend using
internal per-cluster configs when present, and explained fallback
behavior to manual hostname/account/output_dir entry.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

---------

Signed-off-by: Chenjie Luo <chenjiel@nvidia.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.claude/skills/evaluation/SKILL.md

@@ -197,6 +197,17 @@ Reasoning models: prefer reasoning mode (highest scores). For lower variance / c
 
 ### Step 4 — Fill remaining ??? values
 
+**Predefined per-cluster execution config (check FIRST).** Some installs ship `internal/slurm/<cluster>` execution groups (optional `nemo_evaluator_launcher_internal` pkg) that pre-fill hostname/partition/gres — leaving only account/output_dir/walltime. Discover at runtime (nothing cluster-specific hardcoded):
+
+```bash
+python3 -c 'import nemo_evaluator_launcher_internal' 2>/dev/null && \
+PKG=$(python3 -c 'import nemo_evaluator_launcher_internal as m,os;print(os.path.dirname(m.__file__))') && \
+for f in "$PKG"/configs/execution/internal/slurm/*.yaml; do \
+  echo "$(basename "$f" .yaml) -> $(grep -E '^hostname:' "$f" | awk '{print $2}')"; done
+```
+
+Hostname match → set `defaults: - execution: internal/slurm/<cluster>`, drop the redundant `execution.hostname` (keep account/output_dir/walltime), verify with `--dry-run`. Else keep `slurm/default` and fill hostname/account/output_dir manually.
+
 - Find every `???` left. Ask the user only for what can't be inferred (SLURM hostname/account/output_dir, MLflow tracking URI, etc.). Don't propose defaults; let them give plain text.
 - **`parallelism`** — size it yourself from the run shape (total requests = `dataset_size × repeats` vs GPU serving capacity), and set `--max-num-seqs` to match. Read `references/parallelism.md` for the decision rule and worked examples; only ask the user if a non-GPU cap (e.g. judge rate limit) is unknown.
 - Ask about other defaults they may want to change (partition, walltime, MLflow tags).

.claude/skills/evaluation/recipes/examples/example_eval.yaml

@@ -41,6 +41,8 @@
 # parallelism.
 #   nel run --config ... -o ++evaluation.nemo_evaluator_config.config.params.limit_samples=2
 defaults:
+  # slurm/default works anywhere; if your install ships a predefined
+  # internal/slurm/<cluster> config, prefer it (see SKILL.md Step 4).
   - execution: slurm/default
   - deployment: vllm
   - _self_