it prompts for an access token

Hmm - I do not see that myself. Which commands did you run that led you to see this?

a command like

pulumi login file://c:\dev\state

it works great on 0.17.8, on .9 it doesn't seem to interpret that as a file URI

Looks like this is a Windows-specific issue - @helpful-vegetable-35581 reported https://github.com/pulumi/pulumi/issues/2693 on this earlier today and we're looking into it now.