Fix UI freeze: Remove high-frequency logging and throttle scroll effects

Performance optimizations to prevent UI freeze during streaming:

1. message-block-list.tsx:
   - Removed createEffect that logged on every messageIds change
   - Removed unused logger import (was causing IPC overload)

2. multi-task-chat.tsx:
   - Changed filteredMessageIds from function to createMemo for proper memoization
   - Throttled auto-scroll effect to only trigger when message COUNT changes
   - Previously it fired on every reactive store update during streaming

These changes prevent excessive re-renders and IPC calls during message streaming.

packages/ui/src/components/chat/multi-task-chat.tsx

@@ -107,7 +107,7 @@ export default function MultiTaskChat(props: MultiTaskChatProps) {
   };
 
   // Filter messages based on selected task - use store's session messages for the task session
-  const filteredMessageIds = () => {
+  const filteredMessageIds = createMemo(() => {
     const task = selectedTask();
     if (!task) return []; // Show no messages in Pipeline view
 
@@ -119,7 +119,7 @@ export default function MultiTaskChat(props: MultiTaskChatProps) {
 
     // Fallback to task.messageIds for backward compatibility
     return task.messageIds || [];
-  };
+  });
 
   // Note: Auto-scroll is handled in two places:
   // 1. After sending a message (in handleSendMessage)
@@ -229,13 +229,23 @@ export default function MultiTaskChat(props: MultiTaskChatProps) {
     return () => clearInterval(interval);
   });
 
-  // Auto-scroll when new messages arrive
+  // Auto-scroll when new messages arrive (throttled to count changes only)
+  let lastScrolledCount = 0;
   createEffect(() => {
     const ids = filteredMessageIds();
+    const count = ids.length;
     const thinking = isAgentThinking();
 
-    // Scroll when message count changes or when thinking starts (unless user is scrolling)
+    // Only scroll when message COUNT changes, not on every store update
-    if ((ids.length > 0 || thinking) && !userScrolling()) {
+    // This prevents the effect from firing on every streaming chunk
+    if (count !== lastScrolledCount && count > 0 && !userScrolling()) {
+      lastScrolledCount = count;
+      requestAnimationFrame(() => {
+        setTimeout(scrollToBottom, 50);
+      });
+    }
+    // Also scroll when thinking first starts
+    if (thinking && count > 0 && !userScrolling()) {
       requestAnimationFrame(() => {
         setTimeout(scrollToBottom, 50);
       });

packages/ui/src/components/message-block-list.tsx

@@ -1,10 +1,7 @@
-import { Index, type Accessor, createEffect } from "solid-js"
+import { Index, type Accessor } from "solid-js"
 import VirtualItem from "./virtual-item"
 import MessageBlock from "./message-block"
 import type { InstanceMessageStore } from "../stores/message-v2/instance-store"
-import { getLogger } from "../lib/logger"
-
-const log = getLogger("multix-chat")
 
 export function getMessageAnchorId(messageId: string) {
   return `message-anchor-${messageId}`
@@ -31,14 +28,6 @@ interface MessageBlockListProps {
 }
 
 export default function MessageBlockList(props: MessageBlockListProps) {
-  createEffect(() => {
-    const ids = props.messageIds();
-    log.info("[MessageBlockList] messageIds changed", { 
-      count: ids.length,
-      ids: ids.slice(-3) // Log last 3 for context
-    });
-  });
-
   return (
     <>
       <Index each={props.messageIds()}>