Function register_project_diff_provider 

pub fn register_project_diff_provider(services: &ServiceRegistry)

Register the view opener on the generic provider-view seam.

This — plus an ex-command and a transient row, both also in this crate — is the whole of the trigger. No Editor:: method, no host Action variant, no dispatch arm: the acid test a provider crate is supposed to pass.

A missing registry means the host did not publish the seam (an older boot, or a test harness); logged and skipped, because refusing to boot over an unavailable optional surface is the worse failure.