feat(admin): wave metrics split by model version (M6)

The library page compares listen-through, early-skip and like rates per
impression model version, so v1 and the trained ranker can be compared online.

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

apps/web/src/pages/admin/LibraryPage.tsx

@@ -99,6 +99,33 @@ export function LibraryPage() {
               </div>
             ))}
           </div>
+          {d.wave.by_model.length > 1 && (
+            <div className={s.tableWrap}>
+              <table className={s.table}>
+                <caption className={s.muted}>{t('library.wave_by_model')}</caption>
+                <thead>
+                  <tr>
+                    <th scope="col">{t('library.wave_model')}</th>
+                    <th scope="col">{t('library.wave_served')}</th>
+                    <th scope="col">{t('library.wave_listen')}</th>
+                    <th scope="col">{t('library.wave_early_skip')}</th>
+                    <th scope="col">{t('library.wave_likes')}</th>
+                  </tr>
+                </thead>
+                <tbody>
+                  {d.wave.by_model.map((m) => (
+                    <tr key={m.model_ver}>
+                      <td>{m.model_ver || '—'}</td>
+                      <td>{m.served.toLocaleString()}</td>
+                      <td>{pct(m.listen_through_rate)}</td>
+                      <td>{pct(m.early_skip_rate)}</td>
+                      <td>{m.like_rate === null ? '—' : m.like_rate.toFixed(1)}</td>
+                    </tr>
+                  ))}
+                </tbody>
+              </table>
+            </div>
+          )}
         </section>
       )}
       {d && d.sources.length > 0 && (