Preserve nested dataclass targets during instantiation

[omry]

Preserve dataclass instances returned by nested target entries when convert=none inserts them into DictConfig or ListConfig containers. Add regression coverage for nested dict and list containers, including top-level list roots.

Fixes #2507

[Copilot]

Pull request overview

This PR fixes an instantiation edge case where dataclass instances produced by nested _target_ configs could be coerced back into structured DictConfig/ListConfig nodes when _convert_=none returns OmegaConf containers. It does so by explicitly wrapping structured-config objects as AnyNode before inserting them into DictConfig/ListConfig, preserving the instantiated object.

Changes:

• Wrap structured-config (e.g., dataclass) instances in AnyNode(…, allow_objects=True) when inserting into DictConfig/ListConfig for _convert_=none.
• Add regression tests covering nested dict/list containers, including a top-level list root case.
• Add a news fragment and update isort to skip .venv.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
hydra/_internal/instantiate/_instantiate2.py	Preserve structured-config instances in _convert_=none containers by wrapping them as AnyNode before insertion.
tests/instantiate/test_instantiate.py	Updates expected ConvertMode.NONE behavior and adds regression coverage for nested dataclass targets in dict/list containers.
news/2507.bugfix	User-facing bugfix note for the instantiation behavior change.
.isort.cfg	Exclude .venv from isort processing.