Like prefix/suffix stripping, substring and regexp path replacement can
produce a relative path or expose dot segments that later path-scoped
handlers interpret differently. Apply the existing canonicalizePath
safeguard whenever these operations change the path.
Addresses scan report 65568b0d767b733c.
Code written by GitHub Copilot (GPT-6.1 Sol, Claude Opus 5.5); reviewed by mholt.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>