Is there a way yet, in pulumi, to have project-wide configurations vs just stack? without implementing a custom system, copy-pasta is rampant in a lot of our projects unless I use custom map mergers, and do all of the configuration logic in code… which defeats the purpose of even using pulumi’s config system outside of secrets.

The current recommendation is to have a "config" project, with just one stack, and all your project-wide config as outputs. Then all the stacks in your "real" project use stack references on the config project.