macOS: UF2 copy is not detected as complete

[dhalbert]

macOS 26 beta 4 or so, and Chrome 138.0.7204.184. (I don't have another macOS machine that is running the current stable macOS)

Copying a CircuitPython UF2 gets stuck like this:

But the copy has completed: CircuitPython has come up on the board.
The Chrome console log shows this:

I guess the connection disappeared out from under the UF2 copier when the board rebooted.