fix(sglang): keep single column-0 exec in entrypoint for sanity dry-run

Wrapping the terminal exec in an if/else indented both exec lines, so the
sanity test's entrypoint dry-run regex (^exec python3 ...) no longer matched
and TestEntrypointArgHandling execed the real launch_server, timing out (7
errors). Select the launch target into a variable and keep one unindented
exec python3 line, matching the vllm entrypoint convention.

Author: Jyothirmaikottu

scripts/docker/sglang/sagemaker_entrypoint.sh

@@ -56,12 +56,12 @@ if ! [[ " ${ARGS[@]} " =~ " --model-path " ]]; then
     ARGS+=(--model-path "${SM_SGLANG_MODEL_PATH:-/opt/ml/model}")
 fi
 
+# diffusion routes through the wrapper that adds SageMaker's /ping + /invocations routes.
 if [ "$ENGINE" = "diffusion" ]; then
-    # multimodal_gen's server lacks the SageMaker /ping + /invocations routes,
-    # so launch it through the wrapper that adds them.
-    echo "Running command: exec python3 /usr/local/bin/sagemaker_diffusion_serve.py ${ARGS[@]}"
-    exec python3 /usr/local/bin/sagemaker_diffusion_serve.py "${ARGS[@]}"
+    LAUNCH_TARGET=(/usr/local/bin/sagemaker_diffusion_serve.py)
 else
-    echo "Running command: exec python3 -m sglang.launch_server ${ARGS[@]}"
-    exec python3 -m sglang.launch_server "${ARGS[@]}"
+    LAUNCH_TARGET=(-m sglang.launch_server)
 fi
+
+echo "Running command: exec python3 ${LAUNCH_TARGET[@]} ${ARGS[@]}"
+exec python3 "${LAUNCH_TARGET[@]}" "${ARGS[@]}"