fix: harden phase summary open questions

frontend/src/viewers/artifactV2.ts

@@ -119,3 +119,18 @@ export interface PhaseSummaryV2 {
   tables?: PhaseTable[];
   open_questions?: string[];
 }
+
+/** Defensive compatibility for malformed v2 artifacts persisted before the gate
+ * enforced `open_questions: string[]`. New payloads stay strictly typed as strings. */
+export function phaseOpenQuestionText(value: unknown): string | null {
+  if (typeof value === "string") return value.trim() || null;
+  if (typeof value === "number" || typeof value === "boolean") return String(value);
+  if (!value || typeof value !== "object" || Array.isArray(value)) return null;
+
+  const record = value as Record<string, unknown>;
+  for (const field of ["question", "label"]) {
+    const text = record[field];
+    if (typeof text === "string" && text.trim()) return text.trim();
+  }
+  return null;
+}