refactor(detail): extract sections as server components

Moves ~1,300 lines of section markup out of the two client views into
components/school/, mirroring the components/compare/ layout. Twelve section
components plus shared primitives, all server components. The only client
file is AdmissionsViewToggle, which owns the hidden/aria-pressed state and
receives both views as server-rendered children.

JSX was extracted mechanically rather than retyped, so the markup the CSS
modules depend on is verbatim.

Sharing follows measured similarity, not assumption:
- Finances (91%) shared. The secondary premises-cost card is gated behind a
  prop so primary pages are unchanged; enabling it is a one-line follow-up.
- Ofsted (80%) shared, but behind a variant prop. The headline similarity hid
  a real fork: on a school with no overall grade the primary page shows a
  "Not rated" badge while the secondary shows a four-area OEIF panel, and the
  disclaimer copy differs. Both preserved exactly; reconciling them is a
  human decision, not a side effect of a move.
- Admissions (14%) and History (40%) kept separate.

Not yet wired up -- the old views still render.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

nextjs-app/components/school/sectionShared.tsx

@@ -0,0 +1,43 @@
+/**
+ * Shared primitives for the school detail sections, mirroring
+ * components/compare/sectionShared.tsx.
+ *
+ * Deliberately minimal: the sections were extracted as verbatim moves from the
+ * two detail views, so wrapping their markup in heavyweight primitives would
+ * risk changing the DOM the CSS modules depend on. This provides only the
+ * outer <section> shell every section shares, plus the stylesheet.
+ *
+ * All section components are SERVER components — no 'use client' anywhere in
+ * this directory except AdmissionsViewToggle.
+ */
+
+import type { ReactNode } from 'react';
+import styles from './schoolSections.module.css';
+
+export const sectionStyles = styles;
+
+/** Tone class for a progress score: positive, negative, or neutral. */
+export function progressClass(val: number | null | undefined): string {
+  if (val == null) return '';
+  if (val > 0) return styles.progressPositive;
+  if (val < 0) return styles.progressNegative;
+  return '';
+}
+
+/**
+ * The section shell. `id` must match the id buildNavItems emits, because the
+ * sticky nav's scroll-spy locates sections with document.getElementById.
+ */
+export function Section({
+  id,
+  children,
+}: {
+  id: string;
+  children: ReactNode;
+}) {
+  return (
+    <section id={id} className={styles.card}>
+      {children}
+    </section>
+  );
+}