fix(review): accurate PRU/AP copy, unbundle same-school trend, de-dupe note CSS

Three review points on the special-schools change:

1. Copy accuracy — the context note said "Its pupils have special educational
   needs" for every isSpecialSchool() match, but the helper also matches pupil
   referral units and alternative provision, whose pupils are educated outside
   a mainstream setting (e.g. after exclusion) and are not necessarily SEND.
   Extracted a shared <SpecialSchoolNote> with type-aware copy: SEND wording
   only for genuine special schools; PRUs/AP get their own accurate wording.

2. Same-school trend was conflated with the England comparison — SchoolRow's
   year-over-year trend arrow (and the school's own figure) were gated on the
   same flag that drops the vs-England delta, hiding a still-meaningful trend
   for special schools with real data. Split the two: the school's OWN RWM
   figure + trend show whenever there's a real value (special schools
   included; only a placeholder all-zero row is hidden); only the vs-England
   delta is additionally dropped for special/PRU/AP. Mirrored in
   SecondarySchoolRow (own Attainment 8 shown; only the vs-LA delta dropped).

3. De-duplicated the .specialNote CSS (was copy-pasted between the two detail
   view module files) into SpecialSchoolNote.module.css, owned by the shared
   component so it can't drift.

New SpecialSchoolNote unit tests assert SEND wording for special schools and
NOT for PRUs/AP. tsc clean; 112/112 unit.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

nextjs-app/components/SchoolDetailView.tsx

@@ -21,6 +21,7 @@ import {
   formatPercentage, formatProgress, formatAcademicYear, isProposedToClose, ofstedLegacyAreas, isSpecialSchool,
 } from '@/lib/utils';
 import { DeltaChip } from './DeltaChip';
+import { SpecialSchoolNote } from './SpecialSchoolNote';
 import { summariseAdmissions } from '@/lib/compareLogic';
 
 const PerformanceChart = dynamic(
@@ -656,20 +657,10 @@ export function SchoolDetailView({
                   : 'End-of-primary-school tests taken by Year 6 pupils. England averages shown for comparison.'}
           </p>
 
-          {/* Special schools sit the same national assessments but teach pupils
-              with SEND, so very few reach the mainstream "expected standard".
-              Explain that up front and drop the England comparison below, so a
-              0% headline never reads as a failing grade against a benchmark
-              that doesn't fit the school. */}
-          {isSpecial && (
-            <div className={styles.specialNote} role="note">
-              <strong>This is a special school.</strong> Its pupils have special educational
-              needs and work towards individual targets. They sit the same national tests, but
-              very few reach the mainstream &ldquo;expected standard&rdquo; these measures report,
-              so a comparison with the England average isn&rsquo;t a meaningful guide to the
-              school. Where available, the progress pupils make (below) is a fairer measure.
-            </div>
-          )}
+          {/* Explains up front why the England comparison is dropped below, so
+              a 0% headline never reads as a failing grade against a benchmark
+              that doesn't fit. Type-aware copy (special vs PRU vs AP). */}
+          <SpecialSchoolNote school={schoolInfo} />
 
           {/* ── Primary / KS2 content ── */}
           {hasKS2Results && (