Zips the given files (content:// paths included) into a folder of their own
in the app's cache and offers the zip through System_ShareFile. The receiving
app reads it whenever it likes, so it can't be deleted right away: each share
deletes the folders of earlier shares once they're an hour old.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
