I've used Activity Monitor to close every process with the Creative Cloud icon.
I've deleted the Creative Cloud Files directory itself, and deleted it from the trash.
I've gone to the "Extensions" preference pane and turned off "Core Sync."
I've quit Finder and restarted it.
And yet the "Creative Cloud Files" icon still shows up in my Finder sidebar, even though the original can't be found.
How can I eliminate this zombie icon once and for all?