fix(school-detail): hero Ofsted chip mislabels OEIF schools as Report Card

The API returns ``framework`` as the literal string "NULL" for older OEIF
inspections (it comes from the upstream ``event_type_grouping`` column),
not real null. The original render path checks ``=== 'ReportCard'`` and
correctly treats anything else as OEIF — but buildOfstedHeroChip inverted
that and treated anything not exactly equal to ``'OEIF'`` as Report Card,
so OLQH (inspected Nov 2023, Outstanding) was being labelled as a Report
Card school in the hero strip and the at-a-glance tile.

- Invert the helper: only branch into Report Card when framework is
  explicitly ``'ReportCard'``; treat OEIF / null / "NULL" / anything else
  as OEIF, and require ``overall_effectiveness`` to render the grade word.
- Replace the toneClass field (which reused .ofstedGrade{N} / .rcGrade{N}
  badge classes and dragged in their backgrounds) with a clean tone enum
  ``teal | green | gold | coral | neutral``. The serif Ofsted heroStat
  picked up the badge background and rendered as a green box around
  "Report Card" — gone now.
- Hero chip backgrounds use color-mix() against the tone variable so all
  five tones share one rule.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

nextjs-app/lib/utils.ts

@@ -423,59 +423,73 @@ function formatOfstedMonth(date: string | null | undefined): string {
   return d.toLocaleDateString('en-GB', { month: 'long', year: 'numeric' });
 }
 
+export type HeroTone = 'teal' | 'green' | 'gold' | 'coral' | 'neutral';
+
 export interface OfstedHeroChip {
   state: 'oeif' | 'reportCard' | 'none';
   title: string;           // Main label (e.g. "Ofsted Outstanding", "Ofsted Report Card")
   subtitle: string;        // Context line (e.g. "Inspected November 2023")
   detail?: string;         // Optional extra line (e.g. "Safeguarding: Met")
-  toneClass: string;       // CSS class key — matches .ofstedGrade{N} / .rcGrade{N} / neutral
+  tone: HeroTone;          // Maps to dedicated hero tone classes (not badge classes)
 }
 
 /**
  * Build the hero-strip Ofsted chip, branching on the inspection framework.
  * Never synthesises a single overall grade for ReportCard schools.
+ *
+ * Note: the API may return ``framework`` as a literal string ``"NULL"`` for
+ * older inspections, so we explicitly only branch into the ReportCard layout
+ * when the value is exactly ``"ReportCard"``. Anything else with an
+ * ``overall_effectiveness`` score is treated as OEIF.
  */
 export function buildOfstedHeroChip(ofsted: OfstedInspection | null | undefined): OfstedHeroChip {
-  if (!ofsted || !ofsted.framework) {
+  if (!ofsted) {
     return {
       state: 'none',
       title: 'Ofsted pending',
       subtitle: 'No inspection on record',
-      toneClass: 'heroChipNeutral',
+      tone: 'neutral',
     };
   }
 
   const when = formatOfstedMonth(ofsted.inspection_date);
 
-  if (ofsted.framework === 'OEIF') {
-    const grade = ofsted.overall_effectiveness;
-    if (grade && OFSTED_OEIF_WORDS[grade]) {
-      return {
-        state: 'oeif',
-        title: `Ofsted ${OFSTED_OEIF_WORDS[grade]}`,
-        subtitle: when ? `Inspected ${when}` : 'Inspected',
-        toneClass: `ofstedGrade${grade}`,
-      };
-    }
+  // ReportCard branch — only if the API explicitly says so
+  if (ofsted.framework === 'ReportCard') {
+    const safeguarding = ofsted.rc_safeguarding_met;
     return {
-      state: 'oeif',
-      title: 'Ofsted inspected',
-      subtitle: when ? `Inspected ${when}` : 'Inspection on record',
-      toneClass: 'heroChipNeutral',
+      state: 'reportCard',
+      title: 'Ofsted Report Card',
+      subtitle: when ? `Inspected ${when}` : 'New framework inspection',
+      detail:
+        safeguarding == null
+          ? undefined
+          : safeguarding ? 'Safeguarding: Met' : 'Safeguarding: Not met',
+      tone: safeguarding === false ? 'coral' : 'green',
+    };
+  }
+
+  // Otherwise treat as OEIF (covers framework === 'OEIF', null, "NULL", etc.)
+  const grade = ofsted.overall_effectiveness;
+  if (grade && OFSTED_OEIF_WORDS[grade]) {
+    const oeifTone: HeroTone =
+      grade === 1 ? 'teal' :
+      grade === 2 ? 'green' :
+      grade === 3 ? 'gold' :
+      'coral';
+    return {
+      state: 'oeif',
+      title: `Ofsted ${OFSTED_OEIF_WORDS[grade]}`,
+      subtitle: when ? `Inspected ${when}` : 'Inspected',
+      tone: oeifTone,
     };
   }
 
-  // ReportCard — never fabricate an overall grade
-  const safeguarding = ofsted.rc_safeguarding_met;
   return {
-    state: 'reportCard',
-    title: 'Ofsted Report Card',
-    subtitle: when ? `Inspected ${when}` : 'New framework inspection',
-    detail:
-      safeguarding == null
-        ? undefined
-        : safeguarding ? 'Safeguarding: Met' : 'Safeguarding: Not met',
-    toneClass: safeguarding === false ? 'rcGrade5' : 'rcGrade2',
+    state: 'oeif',
+    title: 'Ofsted inspected',
+    subtitle: when ? `Inspected ${when}` : 'Inspection on record',
+    tone: 'neutral',
   };
 }