Address review feedback: guard GITHUB_WORKSPACE, fix comments

- Use ${GITHUB_WORKSPACE:?} to fail fast if variable is unset
- Fix ntasks-per-node comment to say "tasks (MPI ranks)" not "cores"
- Fix monitor script comment: polling-based, not non-blocking

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: sbryngelson

.github/scripts/monitor_slurm_job.sh

@@ -61,7 +61,7 @@ squeue_failures=0
 last_heartbeat=$(date +%s)
 
 while true; do
-  # Try to read from tail output (non-blocking via timeout)
+  # Try to read from tail output with a 1s timeout (polling-based)
   # Read multiple lines if available to avoid falling behind
   lines_read=0
   while IFS= read -r -t 1 line <&3 2>/dev/null; do

.github/workflows/phoenix/submit-bench.sh

@@ -21,7 +21,7 @@ sbatch_cpu_opts="\
 
 sbatch_gpu_opts="\
 #SBATCH --gres=gpu:H200:2
-#SBATCH --ntasks-per-node=8       # Number of cores per node required\
+#SBATCH --ntasks-per-node=8       # Number of tasks (MPI ranks) per node\
 "
 
 if [ "$2" = "cpu" ]; then

.github/workflows/phoenix/submit.sh

@@ -24,7 +24,7 @@ sbatch_cpu_opts="\
 
 sbatch_gpu_opts="\
 #SBATCH --gres=gpu:H200:2
-#SBATCH --ntasks-per-node=8       # Number of cores per node required\
+#SBATCH --ntasks-per-node=8       # Number of tasks (MPI ranks) per node\
 "
 
 if [ "$2" = "cpu" ]; then

.github/workflows/test.yml

@@ -200,7 +200,7 @@ jobs:
       ACTIONS_ALLOW_USE_UNSECURE_NODE_VERSION: true
     steps:
       - name: Clean workspace
-        run: rm -rf "$GITHUB_WORKSPACE"/* "$GITHUB_WORKSPACE"/.[!.]* 2>/dev/null || true
+        run: rm -rf "${GITHUB_WORKSPACE:?}"/* "${GITHUB_WORKSPACE:?}"/.[!.]* 2>/dev/null || true
 
       - name: Clone
         uses: actions/checkout@v4