cli[minor]: Add langgraph new command (#2369)

Adds a "new" command to create langgraph application from a template.

libs/cli/tests/integration_tests/test_cli.py

@@ -0,0 +1,13 @@
+import pytest
+import requests
+
+from langgraph_cli.templates import TEMPLATE_ID_TO_CONFIG
+
+
+@pytest.mark.parametrize("template_key", TEMPLATE_ID_TO_CONFIG.keys())
+def test_template_urls_work(template_key: str) -> None:
+    """Integration test to verify that all template URLs are reachable."""
+    _, _, template_url = TEMPLATE_ID_TO_CONFIG[template_key]
+    response = requests.head(template_url)
+    # Returns 302 on a successful HEAD request
+    assert response.status_code == 302, f"URL {template_url} is not reachable."