Function open_project_diff 

pub fn open_project_diff(
    activator: &mut dyn ModeActivator,
    args: &Args,
) -> ProviderViewOutcome

Open (or re-drive) the project-diff view.

This is the closure registered on the generic provider-view seam, so it is the whole of what the host does for this feature: the host arm looks the name up, calls this with itself as the activator, and applies the returned [ProviderViewOutcome].

The view opens empty and immediately; the scan runs off-thread and streams into it. Re-triggering with the view already open re-drives the scan into the same buffer rather than minting a second one — which is also why the excerpts are cleared here rather than in the task: the clear must be visible before the first batch lands, or the old and new scans briefly show together.