Fix checklist sub-issue workflow gates

- Correct stale assertion in IssuesList.test.tsx to match the real
  workflowSort output: PAP-3 is step 2, not step 1, when PAP-1 is a done
  sibling that shares the ready queue.
- Make the sub-issues-workflow storybook fixture pass typecheck by
  returning Date objects (not ISO strings) from the createdAt helper so
  Issue.createdAt / completedAt types match.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

ui/src/components/IssuesList.test.tsx

@@ -489,7 +489,7 @@ describe("IssuesList", () => {
       expect(rows.filter((row) => row.getAttribute("data-current-step") === "true")).toHaveLength(1);
       expect(rows.find((row) => row.textContent?.includes("Active blocker"))?.getAttribute("data-current-step")).toBe("true");
       expect(rows.find((row) => row.textContent?.includes("Done first"))?.getAttribute("data-title-class")).toContain("text-muted-foreground");
-      expect(container.textContent).toContain("blocked by PAP-3 · step 1");
+      expect(container.textContent).toContain("blocked by PAP-3 · step 2");
     });
 
     act(() => {

ui/storybook/stories/sub-issues-workflow.stories.tsx

@@ -44,7 +44,7 @@ const blockerRef = (issue: Issue): BlockerRef => ({
 
 const baseCreatedAt = new Date("2026-04-10T12:00:00.000Z").getTime();
 const createdAt = (offsetMinutes: number) =>
-  new Date(baseCreatedAt + offsetMinutes * 60_000).toISOString();
+  new Date(baseCreatedAt + offsetMinutes * 60_000);
 
 // Mirrors the PAP-1953 topology called out in the PAP-2189 plan:
 //   1954 Scoping (done)                — root