The browser file picker only queued a name and bytes. When the read
finished, DeckCraft guessed the command and ran it on whichever
document and slide were active, so a picture, sound or outline could
land in the wrong place, and a later pick could finish first.
The request now keeps the document, the slide or master, the operation
and a cancellation id. A completion applies there, or is dropped when
that target is gone or the picker was dismissed.
Co-authored-by: Cursor <cursoragent@cursor.com>
