fix: count pupils as the whole school, not the GCSE year group

fact_performance's total_pupils is the cohort a year's results were
measured on. For a secondary that is Year 11 alone, and the list API sent
it as the card's "pupils": Burntwood showed 245 in search and 1,462 on its
page. The list and place payloads now carry the register's whole-school
count, and nothing when the register has none. Map popups and the compare
basket read the same field.

The header and the wellbeing section fell back to the same results figure
when the census had no record. They now fall back to the register count.
The shell took yearlyData only for that fallback, so the prop is gone and
the results array no longer ships to the client for the chrome.

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

nextjs-app/components/school/SchoolDetailShell.tsx

@@ -34,8 +34,6 @@ import styles from './SchoolDetailShell.module.css';
  */
 export interface SchoolDetailShellProps {
   schoolInfo: School;
-  /** Only for the header's pupil-count fallback. */
-  yearlyData: SchoolResult[];
   census: SchoolCensus | null;
   /** Section list for the sticky nav, computed on the server. */
   navItems: NavItem[];
@@ -44,7 +42,7 @@ export interface SchoolDetailShellProps {
 }
 
 export function SchoolDetailShell({
-  schoolInfo, yearlyData, census, navItems, children,
+  schoolInfo, census, navItems, children,
 }: SchoolDetailShellProps) {
   const router = useRouter();
   const { addSchool, removeSchool, isSelected } = useComparison();
@@ -126,7 +124,6 @@ export function SchoolDetailShell({
   // once on the server (lib/schoolSections) and consumed by the section
   // composers; recomputing them here would duplicate that work for values
   // this component never renders.
-  const latestResults = yearlyData.length > 0 ? yearlyData[yearlyData.length - 1] : null;
   const phase = schoolInfo.phase ?? '';
   const isAllThrough = phase.toLowerCase() === 'all-through';
   const hasLocation = schoolInfo.latitude != null && schoolInfo.longitude != null;
@@ -283,7 +280,9 @@ export function SchoolDetailShell({
                 </span>
               )}
               {(() => {
-                const total = census?.total_pupils ?? latestResults?.total_pupils ?? null;
+                // Never latestResults.total_pupils: that is the results
+                // cohort, which for a secondary is the GCSE year group alone.
+                const total = census?.total_pupils ?? schoolInfo.total_pupils ?? null;
                 if (total == null) return null;
                 return (
                   <span className={styles.headerDetail}>