fix: satisfy lock-file when feature-level index-url is set

[baszalmstra]

Description

A manifest PyPI requirement with no per-package index was treated as "the user wants the default PyPI index" during satisfiability. With a feature-level pypi-options.index-url, the lock-file records the custom URL on each package while the requirement carries no index, so pixi install --locked failed with '<pkg>' requires index <default> but the lock-file has <url>.

Compare the locked package URL against the lock-file's environment-level indexes: (already verified to match the manifest by verify_pypi_indexes) instead of hard-coding default PyPI.

Fixes #6060

How Has This Been Tested?

• Unit tests in pypi.rs:
  • test_pypi_feature_level_index_should_satisfy (reproduces [0.68.0] Unable to use --locked with a non-default index-url #6060; also covers trailing-slash + unrelated-index negative case)
  • test_pypi_extra_index_should_satisfy (package locked from an extra-index-urls entry)
• End-to-end fixture: tests/data/satisfiability/pypi-feature-level-index-url/

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
  • I take responsibility for any AI-generated content in my PR.

Tools: Claude Code

Checklist:

• I have performed a self-review of my own code
• I have added sufficient tests to cover my changes.

[baszalmstra]

@ruben-arts THis is ready!

[ruben-arts]

Can confirm this works! Thanks

[sheevy]

Thanks for this. Would to be possible to release this soon, as it's a regression, which unfortunately falls just after the lock file format change?

[wolfv]

Definitely planning to make a release tomorrow. Do you need it earlier than that? Sorry for the regression.

[sheevy]

Thanks for this. Not at all, I just pinned the pixi version in setup-pixi: pixi-version: v0.67.2.