Lowercasing and slash-preserving path cleaning rewrote invalid UTF-8
bytes as U+FFFD, so the path matcher could evaluate a different path
than the file server opens. Preserve the original bytes in both, keeping
case-insensitive matching for valid Unicode.
Addresses scan report 18c02f60a5b43529.
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>