feat(floating-ai): step 1 — extract shared useAIChat hook

Refactor AIChatPanel to consume the existing useAIChat hook instead of
managing chat state inline. Removes duplicate ChatMessage interface,
inline state (messages, input, isStreaming, streamingContent), and the
65-line handleSend callback, replacing them with a single useAIChat()
call and a thin briefLoading guard wrapper.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/renderer/components/ai/AIChatPanel.tsx

@@ -1,21 +1,15 @@
-import { useState, useEffect, useRef, useCallback } from 'react';
+import { useState, useEffect, useRef, useCallback, useMemo } from 'react';
 import { Sparkles, KeyRound, ArrowUp, ListTodo, TrendingUp, AlertCircle, Lightbulb } from 'lucide-react';
 import ReactMarkdown from 'react-markdown';
 import remarkGfm from 'remark-gfm';
 import { trpc } from '@/lib/trpc';
+import { useAIChat, type ChatContext } from '@/hooks/useAIChat';
 import { Card, CardContent } from '@/components/ui/card';
 import { Button } from '@/components/ui/button';
 import { Badge } from '@/components/ui/badge';
 import { Skeleton } from '@/components/ui/skeleton';
 import { ScrollArea } from '@/components/ui/scroll-area';
 
-interface ChatMessage {
-  id: string;
-  role: 'user' | 'assistant';
-  content: string;
-  error?: boolean;
-}
-
 const SUGGESTION_CHIPS = [
   { icon: ListTodo, label: "What's on my plate today?" },
   { icon: TrendingUp, label: 'Summarize this week' },
@@ -46,10 +40,21 @@ export function AIChatPanel({
   const userNameQuery = trpc.settings.getUserName.useQuery(undefined, { enabled: !!isHomePage });
   const dueTodayQuery = trpc.tasks.dueToday.useQuery(undefined, { enabled: !!isHomePage });
 
-  const [messages, setMessages] = useState<ChatMessage[]>([]);
-  const [input, setInput] = useState('');
-  const [isStreaming, setIsStreaming] = useState(false);
-  const [streamingContent, setStreamingContent] = useState('');
+  const chatContext = useMemo<ChatContext>(
+    () => ({
+      type: contextType,
+      ...(contextType === 'project' && projectId ? { projectId } : {}),
+    }),
+    [contextType, projectId],
+  );
+  const {
+    messages,
+    input,
+    setInput,
+    isStreaming,
+    streamingContent,
+    handleSend: chatHandleSend,
+  } = useAIChat(chatContext);
 
   // Daily brief state (home page only)
   const [dailyBrief, setDailyBrief] = useState<string | null>(null);
@@ -59,8 +64,6 @@ export function AIChatPanel({
 
   const messagesContainerRef = useRef<HTMLDivElement | null>(null);
 
-  const streamingContentRef = useRef('');
-  const chatMutation = trpc.ai.chat.useMutation();
   const briefMutation = trpc.ai.dailyBrief.useMutation();
 
   const scrollToBottom = useCallback(() => {
@@ -116,72 +119,9 @@ export function AIChatPanel({
   }, [isHomePage, hasTokenQuery.data]); // briefMutation excluded — only fire once
 
   const handleSend = useCallback(() => {
-    const trimmed = input.trim();
-    if (!trimmed || isStreaming || briefLoading) return;
-
-    const userMsg: ChatMessage = {
-      id: crypto.randomUUID(),
-      role: 'user',
-      content: trimmed,
-    };
-
-    setMessages((prev) => [...prev, userMsg]);
-    setInput('');
-    setIsStreaming(true);
-    setStreamingContent('');
-    streamingContentRef.current = '';
-
-    const unsubscribe = window.electronAI.onStreamChunk(({ token, done }) => {
-      if (done) {
-        const finalContent = streamingContentRef.current;
-        setMessages((prev) => [
-          ...prev,
-          { id: crypto.randomUUID(), role: 'assistant', content: finalContent },
-        ]);
-        setStreamingContent('');
-        streamingContentRef.current = '';
-        setIsStreaming(false);
-        unsubscribe();
-        return;
-      }
-      streamingContentRef.current += token;
-      setStreamingContent(streamingContentRef.current);
-    });
-
-    chatMutation.mutate(
-      {
-        message: trimmed,
-        context: {
-          type: contextType,
-          ...(contextType === 'project' && projectId ? { projectId } : {}),
-        },
-      },
-      {
-        onSuccess: (data) => {
-          if (data.error) {
-            unsubscribe();
-            setMessages((prev) => [
-              ...prev,
-              { id: crypto.randomUUID(), role: 'assistant', content: data.error!, error: true },
-            ]);
-            setStreamingContent('');
-            streamingContentRef.current = '';
-            setIsStreaming(false);
-          }
-        },
-        onError: (err) => {
-          unsubscribe();
-          setMessages((prev) => [
-            ...prev,
-            { id: crypto.randomUUID(), role: 'assistant', content: err.message || 'An unexpected error occurred.', error: true },
-          ]);
-          setStreamingContent('');
-          streamingContentRef.current = '';
-          setIsStreaming(false);
-        },
-      },
-    );
-  }, [input, isStreaming, briefLoading, contextType, projectId, chatMutation]);
+    if (briefLoading) return;
+    chatHandleSend();
+  }, [briefLoading, chatHandleSend]);
 
   const handleKeyDown = (e: React.KeyboardEvent<HTMLTextAreaElement>) => {
     if (e.key === 'Enter' && !e.shiftKey) {