refactor(useAgent): simplify mutate call in agent update

The previous implementation unnecessarily spread the previous state when only the result is needed. This simplifies the mutation logic while maintaining the same behavior.

src/renderer/src/hooks/agents/useAgent.ts

@@ -24,10 +24,7 @@ export const useAgent = (id: string | null) => {
       try {
         // may change to optimistic update
         const result = await client.updateAgent(form)
-        mutate((prev) => ({
-          ...prev,
-          ...result
-        }))
+        mutate(result)
         window.toast.success(t('common.update_success'))
       } catch (error) {
         window.toast.error(formatErrorMessageWithPrefix(error, t('agent.update.error.failed')))