feat(ms22-p2): add agent selector UI in WebUI (#685)

Co-authored-by: Jason Woltje <jason@diversecanvas.com>
Co-committed-by: Jason Woltje <jason@diversecanvas.com>

apps/web/src/components/chat/Chat.tsx

@@ -9,6 +9,7 @@ import { useWorkspaceId } from "@/lib/hooks";
 import { MessageList } from "./MessageList";
 import { ChatInput, type ModelId, DEFAULT_TEMPERATURE, DEFAULT_MAX_TOKENS } from "./ChatInput";
 import { ChatEmptyState } from "./ChatEmptyState";
+import { AgentSelector } from "./AgentSelector";
 import type { Message } from "@/hooks/useChat";
 
 export interface ChatRef {
@@ -66,6 +67,7 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
   const [selectedModel, setSelectedModel] = useState<ModelId>("llama3.2");
   const [temperature, setTemperature] = useState<number>(DEFAULT_TEMPERATURE);
   const [maxTokens, setMaxTokens] = useState<number>(DEFAULT_MAX_TOKENS);
+  const [selectedAgent, setSelectedAgent] = useState<string | null>(null);
 
   // Suggestion fill value: controls ChatInput's textarea content
   const [suggestionValue, setSuggestionValue] = useState<string | undefined>(undefined);
@@ -88,6 +90,7 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
     temperature,
     maxTokens,
     ...(initialProjectId !== undefined && { projectId: initialProjectId }),
+    ...(selectedAgent !== null && { agent: selectedAgent }),
   });
 
   // Read workspace ID from localStorage (set by auth-context after session check).
@@ -375,6 +378,13 @@ export const Chat = forwardRef<ChatRef, ChatProps>(function Chat(
         }}
       >
         <div className="mx-auto max-w-4xl px-4 py-4 lg:px-8">
+          <div className="mb-3">
+            <AgentSelector
+              selectedAgent={selectedAgent}
+              onChange={setSelectedAgent}
+              disabled={isChatLoading || isStreaming || !user}
+            />
+          </div>
           <ChatInput
             onSend={handleSendMessage}
             disabled={isChatLoading || !user}