FIX Remove duplicate VBLoRAConfig entry from peft.__all__

[SHAI-Akshay-Tripathi]

Description

peft.__all__ listed "VBLoRAConfig" twice (lines 272-273 on main). Duplicate entries in __all__ silently confuse documentation tooling, IDE auto-import, and linters that rely on __all__ to determine the public API surface. It's the only duplicate among the 138 entries — looks like a copy-paste slip from a past edit.

Changes

1. src/peft/__init__.py — remove the duplicate line.
2. tests/test_public_api.py — new test file with two regression tests:
   • test_all_has_no_duplicates — guards against this kind of regression.
   • test_all_names_are_importable — verifies every name in __all__ is actually accessible on the package, catching stale or mistyped entries that would break from peft import *.

Verifying the regression test catches the bug

Per CONTRIBUTING.md, ideally a bug fix is accompanied by a test that fails on the broken code and passes on the fix. To confirm:

# On main, without the __init__.py change:
$ python -m pytest tests/test_public_api.py::TestPublicApi::test_all_has_no_duplicates -v
FAILED — AssertionError: Duplicate names in peft.__all__: {'VBLoRAConfig': 2}

# With the fix applied:
$ python -m pytest tests/test_public_api.py -v
PASSED  test_all_has_no_duplicates
PASSED  test_all_names_are_importable

How to test

python -m pytest tests/test_public_api.py -v
make quality

Both pass locally.