Function resolve_sops_dir 

pub fn resolve_sops_dir(
    workspace_dir: &Path,
    config_dir: Option<&str>,
) -> PathBuf

Resolve the SOPs directory from config, falling back to workspace default.

A relative config_dir (the common case in the documented <workspace>/sops layout) resolves against workspace_dir; an absolute or ~-prefixed value is used as-is (Path::join replaces the base entirely when the joined path is itself absolute).