fix: test-sleep runs forever (tail -f /dev/null) for lifecycle testing

Replaced sleep 180 with tail -f /dev/null so the container
stays running until explicitly stopped. Added hostname echo
for log verification.

recipes/test-sleep/recipe.toml

@@ -1,10 +1,10 @@
 engine = "vllm"
-name = "Test Sleep 3min"
+name = "Test Idle Container"
 docker_image = "alpine:latest"
 model = "noop"
 port = 8000
 
-entrypoint = ["sh", "-c", "'echo started && sleep 180 && echo completed'"]
+entrypoint = ["sh", "-c", "'echo \"[$(hostname)] test-idle ready\" && tail -f /dev/null'"]
 
 args = []