added cors support and started chat client

packages/chat-client/src/hooks/useChat.js

@@ -0,0 +1,90 @@
+import { useState, useCallback, useRef } from 'react';
+import { streamMessage } from '../api/orchestration';
+
+export function useChat({ activeSession, appendMessage, updateLastMessage, refreshSessions }) {
+  const [streaming, setStreaming] = useState(false);
+  const [error, setError] = useState(null);
+  const [lastTokenCount, setLastTokenCount] = useState(0);
+  const [lastModel, setLastModel] = useState(null);
+  const cancelRef = useRef(null);
+
+  const sendMessage = useCallback(async (text, model) => {
+    if (!activeSession || !text.trim() || streaming) return;
+
+    setError(null);
+
+    // 1. Append user bubble immediately
+    appendMessage({
+      id: `user-${Date.now()}`,
+      role: 'user',
+      text,
+    });
+
+    // 2. Append empty assistant bubble — will be filled by stream
+    appendMessage({
+      id: `assistant-${Date.now()}`,
+      role: 'assistant',
+      text: '',
+      streaming: true,
+    });
+
+    setStreaming(true);
+
+    // 3. Open stream
+    cancelRef.current = streamMessage(
+      activeSession.external_id,
+      text,
+      model,
+      {
+        onChunk: (token) => {
+          updateLastMessage(msg => ({
+            ...msg,
+            text: msg.text + token,
+          }));
+        },
+
+        onDone: ({ model: resolvedModel, tokenCount }) => {
+          // Mark bubble as complete
+          updateLastMessage(msg => ({ ...msg, streaming: false }));
+          setLastTokenCount(tokenCount);
+          setLastModel(resolvedModel);
+          setStreaming(false);
+          cancelRef.current = null;
+
+          // Refresh session list so new sessions appear in sidebar
+          refreshSessions();
+        },
+
+        onError: (err) => {
+          updateLastMessage(msg => ({
+            ...msg,
+            text: msg.text || 'Something went wrong.',
+            streaming: false,
+            error: true,
+          }));
+          setError(err.message);
+          setStreaming(false);
+          cancelRef.current = null;
+        },
+      }
+    );
+  }, [activeSession, streaming, appendMessage, updateLastMessage, refreshSessions]);
+
+  const cancelStream = useCallback(() => {
+    if (cancelRef.current) {
+      cancelRef.current();
+      cancelRef.current = null;
+      updateLastMessage(msg => ({ ...msg, streaming: false }));
+      setStreaming(false);
+    }
+  }, [updateLastMessage]);
+
+  return {
+    sendMessage,
+    cancelStream,
+    streaming,
+    error,
+    lastTokenCount,
+    lastModel,
+  };
+}