fix(detail): label which phase all-through admissions figures cover (Batch F)

Final Ofsted/education-expert review of the detail page (Batch F) found one
clarity gap: on an all-through school the Admissions block shows a single
entry point's figures (Hessle's are the Year 7 secondary intake —
admissions.school_phase = "Secondary") but is titled just "Admissions", so a
parent interested in the reception/primary intake could read the Year 7
numbers as the whole school.

Add a phase subtitle for all-through schools ("These figures are for secondary
entry (Year 7)." / "...primary entry (Reception)."). Pure-primary and
pure-secondary pages are unambiguous and unchanged.

Rest of the review verified correct against source payloads: all three Ofsted
regimes (report card / ungraded post-Sept-2024 / carried-forward), England-
average anchoring, gap-honest trend charts (KS2 + KS4), all-through dual-phase
rendering, and the mobile layout.

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

nextjs-app/components/SchoolDetailView.tsx

@@ -887,6 +887,15 @@ export function SchoolDetailView({
               </div>
             )}
           </div>
+          {/* All-through admissions data covers a single entry point (usually the
+              Year 7 secondary intake), not reception — say so, or a parent could
+              read these as the whole-school figures. */}
+          {isAllThrough && admissions.school_phase && (
+            <p className={styles.sectionSubtitle}>
+              These figures are for {admissions.school_phase.toLowerCase()} entry
+              {/secondary/i.test(admissions.school_phase) ? ' (Year 7)' : /primary/i.test(admissions.school_phase) ? ' (Reception)' : ''}.
+            </p>
+          )}
 
           <div className={styles.admissionsViewport}>
             {/* This-year Q&A */}