CLI parser crashes on unparameterized list/dict annotations (x: list); Union[list, str] silently misparses to string

[ManoharPaturi]

Description

Entry points using unparameterized collection annotations cannot be set from the CLI:

• def f(tags: list) + tags=[1, 2, 3] → ListParseError: Invalid list: tuple index out of range
• def f(mapping: dict) + mapping={'a': 1} → DictParseError: Invalid dict: not enough values to unpack
• Optional[list] / Optional[dict] fail the same way through the Union parser
• bare typing.List / typing.Dict crash with IndexError in _maybe_resolve_annotation
• silent misparse: Union[list, str] with value [1, 2] returns the string '[1, 2]' because the failed list parse makes the Union fall through to str

Steps to reproduce

import nemo_run as run

@run.cli.entrypoint(skip_confirmation=True)
def train(tags: list = None):
    print(tags)

if __name__ == "__main__":
    run.cli.main(train)

$ python app.py tags=[1,2,3]
nemo_run.cli.cli_parser.ListParseError: ... Invalid list: tuple index out of range

Expected behavior

tags parses to the list [1, 2, 3] (no element type known → no coercion), matching Python semantics of bare list/dict.

Actual behavior

parse_list/parse_dict index get_args(annotation) unconditionally; get_args(list) is empty, so parsing crashes (or misparses inside a Union).

#558 was a different defect in the same area (PEP-604 dispatch) — these still reproduce on current main.

Environment

nemo-run main (b85eb67), Python 3.12, macOS