chore(deps[libvcs]): track vcs_gitconfig fixture rename

[tony]

Summary

Tracks libvcs's pytest plugin fixture rename (libvcs#528 / libvcs#529).

libvcs renames its gitconfig / hgconfig / set_gitconfig / set_hgconfig pytest fixtures to vcs_gitconfig / vcs_hgconfig / set_vcs_gitconfig / set_vcs_hgconfig to vacate the namespace that collided with the third-party pytest-gitconfig plugin. vcspull only references one of these fixtures (gitconfig, in three places), so the test-side change is small.

Changes

• conftest.py:setup() — autouse fixture now requests vcs_gitconfig
• tests/test_fixtures.py::test_home_contains_gitconfig — parameter rename
• tests/test_fixtures.py::test_pytester_git_commit_in_isolated_run — embedded conftest text updates the parameter name in the spawned pytester run
• pyproject.toml — bump libvcs constraint to >=0.41.0,<0.42.0
• pyproject.toml — add [tool.uv.sources] tracking the libvcs branch until 0.41.0 ships on PyPI; drop this section in a follow-up after libvcs 0.41.0 release
• uv.lock — refresh, pins to libvcs branch commit 74dbbae
• CHANGES — Development entry under v1.60.x

Test plan

• uv lock — resolved 92 packages, libvcs pinned to branch commit
• uv sync --all-extras — clean
• uv run ruff format . / uv run ruff check . — all checks passed
• uv run mypy — no issues found in 86 source files
• uv run pytest — 1028 passed (with 27 syrupy snapshots)

Follow-up

Once libvcs 0.41.0 ships on PyPI, open a follow-up PR removing the [tool.uv.sources] block — the version constraint alone will then resolve correctly from PyPI.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.61%. Comparing base (b6f9d71) to head (3a719a6).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #548   +/-   ##
=======================================
  Coverage   83.61%   83.61%           
=======================================
  Files          29       29           
  Lines        4114     4114           
  Branches      813      813           
=======================================
  Hits         3440     3440           
  Misses        440      440           
  Partials      234      234           

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