Fix literal wrapping with black profile

[paulkagiri]

Summary

• account for the assignment prefix when formatting sorted literals
• use vertical hanging wrapping with trailing commas for black-style literal sorting
• add regression coverage for tuple sorting with the black profile

Fixes #1815

Tests

• python -m pytest tests/unit/test_literal.py -q
• python -m black --target-version py312 --check isort/literal.py tests/unit/test_literal.py
• python -m ruff check isort/literal.py tests/unit/test_literal.py
• git diff --check

[DanielNoord]

Please ensure CI passes before opening pull requests :)

[paulkagiri]

Addressed the CI failures.

Changes made:

• Replaced the dynamic enum attribute access that failed mypy with a type-checker-friendly comparison.
• Applied the repo formatter (ruff format) to the touched files.
• Removed an assert in parser code that Bandit flagged during the lint tox env, while keeping the type narrowing explicit through literal straight / lazy_straight branches.

Validation:

• python -m uv run --with tox-uv tox -e lint
• python -m uv run --with tox-uv tox -e py
• python -m pytest tests/unit/test_literal.py -q
• python -m ruff format --check isort/literal.py tests/unit/test_literal.py
• git diff --check

[DanielNoord]

@paulkagiri Unfortunately it doesn't pass CI again. Are you sure all code added is covered?