Open stats: the chosen window's tab uses the readable accent fill (white on the season's orange was 2.6:1; axe) (#364)

ddiff --git a/server/stats/open.js b/server/stats/open.js
iindex 32c6f3c8..c16d48e3 100644
---- a/server/stats/open.js
++++ b/server/stats/open.js
@@@ -378,7 +378,7 @@ const CSS = `
  .os-lede{margin:0 0 14px;max-width:760px;color:var(--text-secondary);line-height:1.55}
  .os-tabs{display:inline-flex;gap:4px;padding:4px;border-radius:999px;background:var(--bg-secondary);border:1px solid var(--border)}
  .os-tabs a{padding:7px 14px;border-radius:999px;color:var(--text-secondary);text-decoration:none;font-size:.86rem;font-weight:700}
--.os-tabs a[aria-current]{background:var(--accent);color:#fff}
++.os-tabs a[aria-current]{background:var(--accent-strong,var(--accent));color:var(--on-accent-strong,#fff)}
  .os-data{margin:12px 0 0;font-size:.84rem;color:var(--text-muted)}
  .os-tiles{display:grid;grid-template-columns:repeat(auto-fit,minmax(170px,1fr));gap:12px;margin:22px 0 8px}
  .os-tile{position:relative;display:flex;flex-direction:column;gap:4px;padding:16px 16px 14px;border-radius:16px;background:linear-gradient(160deg,color-mix(in srgb,var(--accent) 10%,transparent),transparent 70%),var(--bg-card);border:1px solid var(--border);min-height:112px}