fix: use handleSubmit directly instead of form requestSubmit

Bypass potential React portal form resolution issues by calling
react-hook-form handleSubmit(onFormSubmit)() directly in the
button onClick handler.

web/app/dashboard/agents/_components/edit.tsx

@@ -284,7 +284,7 @@ function AgentEditDialogBody({
           </Button>
           <Button
             type="button"
-            onClick={() => formRef.current?.requestSubmit()}
+            onClick={() => handleSubmit(onFormSubmit)()}
             disabled={saving || loading}
           >
             {saving ? "保存中..." : "保存"}