## Summary
**What is the goal of this PR?**
Probable fix for #1118. `sanitizeFilename` was only passing through
ASCII characters from filenames. It now maintains valid UTF-8
codepoints, including non-ASCII multibyte sequences. Truncation happens
at a maximum number of bytes, rather than characters, to prevent
filenames with many multibyte sequences from unexpectedly exceeding
FAT32 limits.
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### AI Usage
While CrossPoint doesn't have restrictions on AI tools in contributing,
please be transparent about their usage as it
helps set the right context for reviewers.
Did you use AI tools to help write this code? _**YES, I described #1118
to Claude and it suggested sanitizeFilename as the likely cause**_
Zach Nelson
8ab2f22730