feat: expose invocation ID as NEL_INVOCATION_ID env var (#894)

## Summary
- Exports `NEL_INVOCATION_ID` environment variable at the top of both
docker (local) and slurm execution scripts
- Allows downstream tooling to reference the invocation ID during
evaluation runs

## Test plan
- [ ] Verify docker `run.sh` contains `export NEL_INVOCATION_ID=...` at
the top
- [ ] Verify slurm `run.sub` contains `export NEL_INVOCATION_ID=...`
after `TASK_DIR`
- [ ] Run a local dry-run and inspect generated script

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

---------

Signed-off-by: Alex Gronskiy <agronskiy@nvidia.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: agronskiy

packages/nemo-evaluator-launcher/src/nemo_evaluator_launcher/executors/local/executor.py

@@ -297,6 +297,7 @@ def execute_eval(cls, cfg: DictConfig, dry_run: bool = False) -> str:
                     auto_export_config_str=auto_export_config_str,
                     extra_docker_args=extra_docker_args,
                     endpoint_readiness_timeout=endpoint_readiness_timeout,
+                    invocation_id=invocation_id,
                 ).rstrip("\n")
                 + "\n"
             )
@@ -316,6 +317,7 @@ def execute_eval(cls, cfg: DictConfig, dry_run: bool = False) -> str:
                     auto_export_config_str=auto_export_config_str,
                     extra_docker_args=extra_docker_args,
                     endpoint_readiness_timeout=endpoint_readiness_timeout,
+                    invocation_id=invocation_id,
                 ).rstrip("\n")
                 + "\n"
             )

packages/nemo-evaluator-launcher/src/nemo_evaluator_launcher/executors/local/run.template.sh

@@ -14,6 +14,8 @@
 # limitations under the License.
 
 
+NEL_INVOCATION_ID="{{ invocation_id }}"
+
 # check if docker exists
 command -v docker >/dev/null 2>&1 || { echo 'docker not found'; exit 1; }
 

packages/nemo-evaluator-launcher/src/nemo_evaluator_launcher/executors/slurm/executor.py

@@ -702,6 +702,7 @@ def _create_slurm_sbatch_script(
     s += "#SBATCH --output {}\n".format(remote_task_subdir / "logs" / "slurm-%A.log")
     s += "\n"
     s += f'TASK_DIR="{str(remote_task_subdir)}"\n'
+    s += f'NEL_INVOCATION_ID="{invocation_id}"\n'
     s += "\n"
 
     # Collect env vars using unified pipeline