Carry optional prompt labels through results

smoke_diagnostics.go

@@ -116,9 +116,10 @@ type SmokeTestTarget struct {
 	// ProfileID is the selected profile, if any.
 	ProfileID string
 	// PromptID identifies the selected prompt; PromptVersion carries its
-	// descriptive version label, if any.
+	// descriptive version label. Nil means absent while a non-nil empty string is
+	// explicit. The pointer belongs to this returned target.
 	PromptID      string
-	PromptVersion string
+	PromptVersion *string
 	// DefaultSourceBackendID identifies the backend whose configured default
 	// selected the profile, when that selection path was used.
 	DefaultSourceBackendID string
@@ -305,7 +306,7 @@ func fromDomainSmokeTestReport(report domain.SmokeTestReport) (*SmokeTestReport,
 			BackendID:              report.Target.BackendID,
 			ProfileID:              report.Target.ProfileID,
 			PromptID:               report.Target.PromptID,
-			PromptVersion:          report.Target.PromptVersion,
+			PromptVersion:          copyStringPtr(report.Target.PromptVersion),
 			DefaultSourceBackendID: report.Target.DefaultSourceBackendID,
 			SelectionSource:        report.Target.SelectionSource,
 			Endpoint:               report.Target.Endpoint,