[Code scan] Make example template_script references self-contained and tested

[njzjz]

Found by Codex global repository scan of deepmodeling/dpgen2 at commit 2679611a3704f5c2646c8cb353e34177518db758.

Workflow submission reads train.template_script from disk immediately:

dpgen2/dpgen2/entrypoint/submit.py

Lines 555 to 561 in 2679611

	type_map = config["inputs"]["type_map"]
	numb_models = config["train"]["numb_models"]
	template_script_ = config["train"]["template_script"]
	if isinstance(template_script_, list):
	template_script = [json.loads(Path(ii).read_text()) for ii in template_script_]
	else:
	template_script = json.loads(Path(template_script_).read_text())

Several examples point template_script at train.json, but their example directories do not include that file. Examples include:

dpgen2/examples/calypso/input.test.json

Line 392 in 2679611

"template_script": "train.json",

dpgen2/examples/ch4/input_dist.json

Line 132 in 2679611

"template_script": "train.json",

dpgen2/examples/diffcsp/dpgen.json

Line 385 in 2679611

"template_script": "train.json",

dpgen2/examples/water/input_dpgen.json

Line 372 in 2679611

"template_script": "train.json",

The current example test only loads and normalizes the JSON, so it does not catch missing referenced files:

dpgen2/tests/test_check_examples.py

Lines 30 to 36 in 2679611

	class TestExamples(unittest.TestCase):
	def test_arguments(self):
	for fn in input_files:
	with self.subTest(fn=fn):
	with open(fn) as f:
	jdata = json.load(f)
	normalize(jdata)

Suggested fix: make examples self-contained by pointing at files that exist in their directories, add the missing templates, or enhance the example test to resolve and validate template_script paths.