Function preflight_existing_project_binding 

pub(crate) fn preflight_existing_project_binding(
    db_path: &Path,
    root: &Path,
) -> Result<(), CliError>

Refuse an existing database binding before init writes.

The storage owner performs one read-only admission for both current native identities and supported predecessor metadata. Fresh databases remain available to the initializer, while the later writer still revalidates under its transaction for races.