Issue Description

When running the full Pester test suite, list-changed-files.ps1 and read-diff.ps1
in the PR reference skill report 0% code coverage despite all tests passing. Running
each script's tests in isolation shows expected coverage (90%+).

The root cause appears to be a duplicate function name (Get-RepositoryRoot) defined
in all three scripts, which interferes with Pester's coverage instrumentation when
tests run together.

Additional Context

No response