fix: clarify missing reme launcher env

[haosenwang1018]

Summary

• fail fast with a clear error when --with-reme is used without REME_PATH / REME_SCRIPT
• add focused launcher tests covering both all-missing and partially-missing ReMe env vars
• clean up adjacent launcher lint issues encountered while validating the change

Testing

• uv run python -m pytest tests/test_launcher.py -q
• uv run ruff check launcher.py tests/test_launcher.py
• uv run ruff format --check launcher.py tests/test_launcher.py
• git diff --check

[gemini-code-assist]

Code Review

This pull request primarily focuses on code formatting improvements and the addition of environment variable validation for service launching. Key changes include standardizing string quotes, improving line-wrapping for readability, and updating the pty_launch function to raise a RuntimeError if required path or script environment variables are missing. New unit tests were added to verify this validation logic. Review feedback identifies a potential AttributeError when parsing the YAML configuration if the trainer key is missing, and points out a copy-paste error in the help text for the --db command-line argument.

[gemini-code-assist]

This block has a potential AttributeError on line 310. If the trainer key is missing or null in the YAML config, config.get("trainer") can be None, and None.get("experiment_name") will crash the program. The logic to determine exp_name is also unnecessarily complex and contains redundant code. The suggested change fixes the crash and simplifies the logic.

Suggested change

	exp_name = config.get("trainer").get("experiment_name")
	if exp_name is None or exp_name == "read_yaml_name":
	if exp_name is not None:
	exp_name = exp_name.replace("|", "-")
	exp_name = os.path.basename(yaml_path).replace(".yaml", "")
	else:
	exp_name = exp_name.replace('|', '-')
	exp_name = exp_name.replace("|", "-")
	trainer_config = config.get("trainer") or {}
	exp_name = trainer_config.get("experiment_name")
	if exp_name is None or exp_name == "read_yaml_name":
	exp_name = os.path.basename(yaml_path).replace(".yaml", "")
	else:
	exp_name = exp_name.replace("|", "-")

[gemini-code-assist]

The help text for the --db argument is "Path to configuration file", which appears to be a copy-paste error from the --conf argument. Based on its usage, this argument is for setting debug tags. Please update the help text to reflect its actual purpose.

Suggested change

	"--db", type=str, default="", required=False, help="Path to configuration file"
	"--db", type=str, default="", required=False, help="Enable debug mode and set debug tags",