- FilenameSanitizer class doc previously attributed the bug to "shell
globbing, URI handling, and various download clients"; that was
speculation about the mechanism. The confirmed cause is a failure
inside the Bezzad Downloader NuGet package on Linux. Rewrite the
class doc to describe what we actually know.
- SanitizeFilenameIfEnabled / SanitizePathIfEnabled said "returns it
unchanged" when disabled, which isn't accurate for null input: we
coerce to String.Empty so the return stays non-null. Spell that out.
- SanitizeFilename method summary rewritten to list exactly what it
does rather than "problematic characters".
- Changelog entry said the setting is "on by default" but the default
is OperatingSystem.IsLinux(). Fix the wording.
f0a824d79a