copy(web): replace em dashes in public copy

Rewrites every visitor-facing string that used an em dash, choosing the
punctuation for what the dash was doing: a colon before a list or
explanation, a comma for an aside, a full stop between two thoughts,
parentheses for an aside mid-sentence. Covers page titles and meta
descriptions, the home and admissions guide copy, school page headings
and notes, the compare page, metric labels and tooltips.

Two rewrites also fix the sentence around them: the closure banner no
longer repeats "proposed for closure", and the cut-off caveat's list of
priorities now parses.

A lone dash marking a missing value in a table cell stays: it is a data
convention, not prose. A Jest guard walks the source with the TypeScript
parser and fails on any other em dash in a string or JSX text node.

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

nextjs-app/components/HowItWorksSection.tsx

@@ -47,7 +47,7 @@ export function HowItWorksSection() {
       <div className={styles.sectionHead}>
         <p className={styles.sectionKicker}>Every school page</p>
         <h2 className={styles.sectionHeading}>What you&apos;ll see on every school</h2>
-        <p className={styles.sectionAside}>Primary or secondary — the page adapts to the phase</p>
+        <p className={styles.sectionAside}>The page adapts to primary or secondary</p>
       </div>
       <div className={styles.hiwGrid}>
         {/* Card 1 — Performance */}
@@ -123,7 +123,7 @@ export function HowItWorksSection() {
           <div className={styles.hiwCardBody}>
             <div className={styles.hiwStep}>Judgement</div>
             <div className={styles.hiwTitle}>Ofsted at a glance</div>
-            <p className={styles.hiwDesc}>Since November 2025, Ofsted rates each area of school life on a five-point scale rather than one overall word. We show every area and the inspection date — and, for schools not yet reinspected, the older overall grade they still carry.</p>
+            <p className={styles.hiwDesc}>Since November 2025, Ofsted rates each area of school life on a five-point scale rather than one overall word. We show every area, the inspection date and, for schools not yet reinspected, the older overall grade they still carry.</p>
           </div>
         </div>
 
@@ -152,7 +152,7 @@ export function HowItWorksSection() {
             {/* One verb for one feature. The site previously called this
                 "compare" in the nav, "shortlist" in the footer and "pin" here,
                 which reads as three separate things it does not have. */}
-            <p className={styles.hiwDesc}>Compare up to five schools and every metric aligns in the same columns — works for primary and secondary alike.</p>
+            <p className={styles.hiwDesc}>Compare up to five schools and every metric aligns in the same columns. It works for primary and secondary alike.</p>
           </div>
         </div>
       </div>