fix(ofsted): badge and compare read the grade still in force

Search badges date a grade by the inspection that awarded or confirmed it (ofsted_grade_date) and say 'Inspected · year' when the latest inspection gave no grade. ofstedDisplay's kinds become graded / confirmed / no_overall_grade, read from current_grade rather than a carried-forward overall_effectiveness. lib/ofstedStatus.ts holds the two sentences the school and compare pages share.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

nextjs-app/lib/ofstedStatus.ts

@@ -0,0 +1,48 @@
+/**
+ * The sentences the school page and the compare page print about where an
+ * Ofsted grade came from and what the latest visit was. One wording, two pages.
+ * Rule: docs/superpowers/specs/2026-10-05-ofsted-current-status-design.md
+ */
+
+import type { OfstedCurrentGrade, OfstedInspection, OfstedLatestVisit } from './types';
+
+export function formatOfstedDate(iso: string | null | undefined): string {
+  if (!iso) return '';
+  const d = new Date(iso);
+  if (Number.isNaN(d.getTime())) return '';
+  return d.toLocaleDateString('en-GB', { day: 'numeric', month: 'long', year: 'numeric' });
+}
+
+const VISIT_KIND: Record<OfstedLatestVisit['kind'], string> = {
+  report_card: 'Report card inspection',
+  graded: 'Graded inspection',
+  ungraded: 'Ungraded inspection',
+};
+
+/** "Graded inspection, 6 July 2016" or "Confirmed at an ungraded inspection, 14 March 2023". */
+export function gradeSourceLine(current: OfstedCurrentGrade): string {
+  const when = formatOfstedDate(current.date);
+  const what = current.basis === 'confirmed' ? 'Confirmed at an ungraded inspection' : 'Graded inspection';
+  return when ? `${what}, ${when}` : what;
+}
+
+/** "Ungraded inspection, 13 November 2024: Standards maintained". */
+export function latestVisitLine(visit: OfstedLatestVisit): string {
+  const head = `${VISIT_KIND[visit.kind]}, ${formatOfstedDate(visit.date)}`;
+  return visit.outcome ? `${head}: ${visit.outcome}` : head;
+}
+
+/**
+ * Whether the latest visit needs its own line: when it is not where the grade
+ * came from, or when there is no grade but an ungraded outcome to report. A
+ * graded visit without a grade is already dated by the section title.
+ */
+export function showLatestVisitLine(
+  ofsted: Pick<OfstedInspection, 'current_grade' | 'latest_visit'>,
+): boolean {
+  const visit = ofsted.latest_visit;
+  if (!visit || visit.kind === 'report_card') return false;
+  const current = ofsted.current_grade;
+  if (current) return current.date !== visit.date;
+  return visit.kind === 'ungraded';
+}