Fix stale Beta tab showing a superseded prerelease

GitHub never clears the prerelease flag once a beta ships as stable,
so the latest prerelease can be older than the latest stable release.
Compare publish dates and fall back to the empty state when stable is
newer.

Assisted by Claude Sonnet 5 <noreply@anthropic.com>

website/src/_data/beta.js

@@ -12,6 +12,13 @@ const RELEASES_URL = `https://github.com/${REPO}/releases`;
  * prerelease flag, but that flag is exactly what this workflow sets, and
  * nothing else in this repository publishes prereleases, so it is a safe
  * signal to use here.
+ *
+ * A prerelease flag alone isn't enough though: GitHub never clears
+ * `prerelease` once the corresponding Stable version has actually shipped,
+ * so the latest prerelease can be stale (e.g. beta-1.41-rc04 published
+ * 2026-06-30, followed by Stable v1.41.0 on 2026-07-01). If the newest
+ * Stable release is more recent than the newest prerelease, there is no
+ * current beta and the empty state should be shown instead.
  */
 async function fetchLatestBetaRelease() {
     const headers = { Accept: "application/vnd.github+json" };
@@ -29,7 +36,18 @@ async function fetchLatestBetaRelease() {
 
         const releases = await res.json();
 
-        return releases.find((release) => release.prerelease && !release.draft) || null;
+        const latestBeta = releases.find((release) => release.prerelease && !release.draft) || null;
+        const latestStable = releases.find((release) => !release.prerelease && !release.draft) || null;
+
+        if (!latestBeta) {
+            return null;
+        }
+
+        if (latestStable && latestStable.published_at > latestBeta.published_at) {
+            return null;
+        }
+
+        return latestBeta;
     } catch (err) {
         console.warn(
             `[beta] Could not load the latest beta release. ` +