A diff line carries the absolute path of its file, and both panels
acting on such a line turn it into the repo-relative one git speaks
themselves. Opening a line in a pull request needs that path too, to
name the file to GitHub by it.
Extract repoRelativePath, and have both panels use it. The files panel
gains the check for a path outside the repo that the other one had; a
path it used to pass on matches no file of the working tree either.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>