Offers a file through the system share sheet, for things like sending a
zipped savestate to a friend. Android for now (SYSPROP_SUPPORTS_SHARE_FILE):
content:// paths from a picked folder are shared as they are, and plain paths
through a FileProvider. Either way the receiving app can read just that file.
With no MIME type given, it's guessed from the extension.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
