fix: move defaultCreateValues to separate file to fix HMR

AgentConfigForm.tsx exported both React components and a plain
object constant (defaultCreateValues), which broke Vite Fast Refresh.
Moved the constant to agent-config-defaults.ts so the component
module only exports React components.

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

ui/src/components/NewAgentDialog.tsx

@@ -24,11 +24,8 @@ import {
 } from "lucide-react";
 import { cn } from "../lib/utils";
 import { roleLabels } from "./agent-config-primitives";
-import {
-  AgentConfigForm,
-  defaultCreateValues,
-  type CreateConfigValues,
-} from "./AgentConfigForm";
+import { AgentConfigForm, type CreateConfigValues } from "./AgentConfigForm";
+import { defaultCreateValues } from "./agent-config-defaults";
 import { getUIAdapter } from "../adapters";
 
 export function NewAgentDialog() {