Fix AI Assistant restart to prevent token waste

When clicking 'Restart Chat', the LLM provider was still receiving the
entire conversation history in API calls, wasting tokens and increasing
costs.

Root cause: @openassistant library uses singleton instances that persist
across React component remounts, maintaining internal messageHistory.

Solution:
- Extract restartChat function from useAssistant hook
- Call it to clear library's internal singleton message cache
- Force React component remount using key prop
- Clear Redux message state

This eliminates token waste and reduces API costs for all users.

Signed-off-by: Akash Rai <akashtooop@gmail.com>

Author: akashrai2003

src/ai-assistant/src/components/ai-assistant-component.tsx

@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: MIT
 // Copyright contributors to the kepler.gl project
 
-import React, {useEffect, useState} from 'react';
+import React, {useEffect, useRef, useState} from 'react';
 import {useDispatch, useSelector} from 'react-redux';
 import styled from 'styled-components';
 import {textColorLT, theme} from '@kepler.gl/styles';
@@ -59,6 +59,8 @@ export function AiAssistantComponent() {
 
   const [ideas, setIdeas] = useState<{title: string; description: string}[]>([]);
 
+  const [restartKey, setRestartKey] = useState<number>(0);
+
   // get dataset meta data and re-initialize assistant when datasets or layers change
   useEffect(() => {
     const metaData = getDatasetContext(visState?.datasets, visState?.layers || []);
@@ -70,7 +72,12 @@ export function AiAssistantComponent() {
   const instructions = `${INSTRUCTIONS}\n\n${datasetMetaData}`;
 
   // generate ideas from LLM
-  const {temporaryPrompt} = useAssistant({...assistantProps, instructions});
+  const {temporaryPrompt, restartChat: libraryRestartChat} = useAssistant({...assistantProps, instructions});
+  
+  const restartChatRef = useRef(libraryRestartChat);
+  useEffect(() => {
+    restartChatRef.current = libraryRestartChat;
+  }, [libraryRestartChat]);
 
   const generateIdeas = async () => {
     try {
@@ -97,9 +104,16 @@ export function AiAssistantComponent() {
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [datasetMetaData]);
 
-  const onRestartAssistant = () => {
-    // clean up aiAssistant state
+  const onRestartAssistant = async () => {
     dispatch(updateAiAssistantMessages([]));
+    
+    try {
+      await restartChatRef.current();
+    } catch (e) {
+      console.error('Error restarting chat:', e);
+    }
+    
+    setRestartKey(prev => prev + 1);
   };
 
   const onMessagesUpdated = (messages: MessageModel[]) => {
@@ -117,6 +131,7 @@ export function AiAssistantComponent() {
   return (
     <StyledAiAssistantComponent className="ai-assistant-component">
       <AiAssistant
+        key={restartKey}
         {...assistantProps}
         instructions={instructions}
         theme={theme.textColor === textColorLT ? 'light' : 'dark'}