feat(tests): reopen rejected test keeps all content + rejection notes

Backend (reopen_test):
- Preserve red/blue validation NOTES — teams see exactly what to fix
  without losing the rejection context. Previously both notes were cleared.
- Preserve all content fields: procedure_text, tool_used, red_summary,
  attack_success, blue_summary, detection_result (already the case).
- Preserve evidences (separate table, unaffected — already the case).
- Still clear: validation statuses + who/when validated (fresh re-validation
  required). Phase timing reset so the new execution starts clean.

Frontend:
- Button label: 'Reopen Test' → 'Continue Test' (more accurate intent)
- Dialog title: 'Reopen Test' → 'Continue Test'
- Dialog message: replaces alarming 'workflow will be restarted / clear all'
  with accurate description of what is preserved vs reset
- Toast: explains what to do next

frontend/src/pages/TestDetailPage.tsx

@@ -230,7 +230,7 @@ export default function TestDetailPage() {
     onSuccess: () => {
       invalidateAll();
       setConfirmReopen(false);
-      showToast("Test reopened", "success");
+      showToast("Test returned to Draft — address the feedback and resubmit", "success");
     },
     onError: (err: unknown) => {
       setConfirmReopen(false);
@@ -587,9 +587,9 @@ export default function TestDetailPage() {
       {/* Confirm Reopen Dialog */}
       <ConfirmDialog
         open={confirmReopen}
-        title="Reopen Test"
-        message="This will move the test back to Draft state and clear all validation decisions. The Red/Blue workflow will need to be restarted. Are you sure?"
-        confirmLabel="Reopen"
+        title="Continue Test"
+        message="The test will return to Draft so you can address the rejection feedback. All content is preserved — procedure, summaries, evidences and rejection notes. Only the validation decisions are cleared so leads can re-validate the updated submission."
+        confirmLabel="Continue"
         variant="warning"
         isLoading={reopenMutation.isPending}
         onConfirm={() => reopenMutation.mutate()}