Following lane: don't bounce out of it when editing lanes

Per Codex: saveLanes() bounced to Highlights if the current view wasn't in the
customizable keys, but Following is a special pinned lane (like today/latest)
that's never in keys. Add it to the special-lanes exclusion so editing the lane
picker while viewing Following no longer navigates away.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/routes/+page.svelte

@@ -165,8 +165,9 @@
     prefs.data.lanes = keys;
     persistPrefs();
     // If the reader unpinned the lane they're viewing, fall back to Highlights.
-    // (The pinned Highlights/Latest lanes are never in `keys`, so don't bounce.)
-    if (selected !== 'today' && selected !== 'latest' && !keys.includes(selected)) navigate('today');
+    // (The special pinned lanes — Highlights/Latest/Following — are never in
+    // `keys`, so don't bounce away from them.)
+    if (!['today', 'latest', 'following'].includes(selected) && !keys.includes(selected)) navigate('today');
   }
 
   // Hero is the only image slot; if its image won't load, promote the next one.