when pulumi posts a preview back to the PR, it's just a summary, which shows that a thing will change but not how it will change -- you still have to click in to each summary to see the real diff. is there any way to get deployments to post a diff instead? if not, is that feature planned for the future?

This is currently not possible, but this has been requested and we have an open issue. Please upvote so we can prioritize accordingly! https://github.com/pulumi/pulumi-cloud-requests/issues/120