fix(detail): filter Ofsted sentinel codes, show sixth-form judgement, label carried-forward grades

Batch A of applying compare-screen learnings to the detail page (points 2-3):

- Point 2: the legacy OEIF sub-judgement grid rendered any non-null value
  via OFSTED_LABELS[value], so Ofsted's sentinel code 9 ('not applicable')
  leaked as an undefined label, and the sixth-form judgement was dropped
  entirely. New shared ofstedLegacyAreas() helper returns only real grades
  (1-4) and includes Sixth Form provision. Both detail views + the
  all-same-grade check use it.
- Point 3: the OEIF disclaimer always claimed 'Ofsted no longer makes an
  overall judgement' even when showing a carried-forward grade. It's now
  grade_source-aware and labels carried-forward grades as such, matching
  the compare screen.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

nextjs-app/components/SecondarySchoolDetailView.tsx

@@ -23,7 +23,7 @@ import type {
   SchoolAdmissions, SenDetail, Phonics,
   SchoolDeprivation, SchoolFinance, NationalAverages,
 } from '@/lib/types';
-import { formatPercentage, formatProgress, formatAcademicYear, formatAgeRange, isProposedToClose } from '@/lib/utils';
+import { formatPercentage, formatProgress, formatAcademicYear, formatAgeRange, isProposedToClose, ofstedLegacyAreas } from '@/lib/utils';
 import { DeltaChip } from './DeltaChip';
 import { track, getNavigationSource } from '@/lib/analytics';
 import styles from './SecondarySchoolDetailView.module.css';
@@ -201,17 +201,12 @@ export function SecondarySchoolDetailView({
     : ofsted?.inspection_date ?? null;
 
   // ── Ofsted: detect if all OEIF sub-grades match the overall ───────────
-  const oeifAllSameGrade = (() => {
-    if (!ofsted || isReportCard) return false;
-    const subs = [
-      ofsted.quality_of_education,
-      ofsted.behaviour_attitudes,
-      ofsted.personal_development,
-      ofsted.leadership_management,
-      ...(ofsted.early_years_provision != null ? [ofsted.early_years_provision] : []),
-    ].filter((v): v is number => v != null);
-    return subs.length >= 3 && subs.every(v => v === ofsted.overall_effectiveness);
-  })();
+  const oeifAreas = ofsted ? ofstedLegacyAreas(ofsted) : [];
+  const oeifAllSameGrade =
+    !!ofsted &&
+    !isReportCard &&
+    oeifAreas.length >= 3 &&
+    oeifAreas.every((a) => a.value === ofsted.overall_effectiveness);
 
   // National Attainment 8 baseline for the "Results Over Time" chart.
   const heroAtt8Nat = secondaryAvg.attainment_8_score ?? null;
@@ -404,7 +399,9 @@ export function SecondarySchoolDetailView({
                 )}
               </div>
               <p className={styles.ofstedDisclaimer}>
-                From September 2024, Ofsted no longer makes an overall effectiveness judgement in inspections.
+                {ofsted.grade_source === 'ungraded_carried_forward'
+                  ? 'This overall grade is carried forward from an earlier inspection — Ofsted has since visited without issuing a new overall grade. From September 2024, Ofsted no longer makes an overall effectiveness judgement.'
+                  : 'From September 2024, Ofsted no longer makes an overall effectiveness judgement in inspections.'}
               </p>
               {oeifAllSameGrade ? (
                 <p className={styles.ofstedAllSame}>
@@ -412,15 +409,7 @@ export function SecondarySchoolDetailView({
                 </p>
               ) : (
                 <div className={styles.metricsGrid}>
-                  {[
-                    { label: 'Quality of Teaching', value: ofsted.quality_of_education },
-                    { label: 'Behaviour in School', value: ofsted.behaviour_attitudes },
-                    { label: 'Pupils\' Wider Development', value: ofsted.personal_development },
-                    { label: 'School Leadership', value: ofsted.leadership_management },
-                    ...(ofsted.early_years_provision != null
-                      ? [{ label: 'Early Years (Reception)', value: ofsted.early_years_provision }]
-                      : []),
-                  ].map(({ label, value }) => value != null && (
+                  {oeifAreas.map(({ label, value }) => (
                     <div key={label} className={styles.metricCard}>
                       <div className={styles.metricLabel}>{label}</div>
                       <div className={`${styles.metricValue} ${styles[`ofstedGrade${value}`]}`}>