fix(electrobun): replace tick() with requestAnimationFrame in AgentPane

tick() inside $effect triggers effect re-entry: flush_effects → tick →
flushSync → flush_effects → infinite loop (effect_update_depth_exceeded).
requestAnimationFrame defers DOM scroll to next frame outside the effect.

ui-electrobun/src/mainview/AgentPane.svelte

@@ -40,7 +40,8 @@
 
   $effect(() => {
     void messages.length;
-    tick().then(() => {
+    // Use requestAnimationFrame instead of tick() to avoid effect re-entry cycle
+    requestAnimationFrame(() => {
       if (scrollEl) scrollEl.scrollTop = scrollEl.scrollHeight;
     });
   });