fix: add tool repository credentials to uv build in tool publish (#5223)

* fix: add tool repository credentials to uv build in tool publish

When running 'uv build' during tool publish, the build process now has access
to tool repository credentials. This mirrors the pattern used in run_crew.py,
ensuring private package indexes are properly authenticated during the build.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix: add env kwarg to subprocess.run mock assertions in publish tests

The actual code passes env= to subprocess.run but the test assertions
were missing this parameter, causing assertion failures.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

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Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>