Fix: The placeholder in PromptEditor is obscured. (#14179)

### What problem does this PR solve?

Fix: The placeholder in PromptEditor is obscured.
### Type of change

- [x] Bug Fix (non-breaking change which fixes an issue)

web/src/pages/agent/form/components/prompt-editor/index.tsx

@@ -184,7 +184,7 @@ export const PromptEditor = forwardRef(function PromptEditor(
     onChange,
     onBlur,
     placeholder,
-    showToolbar,
+    showToolbar = true,
     multiLine = true,
     enablePathQueryAutoMerge = true,
     extraOptions,
@@ -237,10 +237,10 @@ export const PromptEditor = forwardRef(function PromptEditor(
           placeholder={
             <div
               className={cn(
-                '-z-10 absolute top-4 left-2 text-text-disabled pointer-events-none',
+                '-z-10 absolute top-1 left-2 text-text-disabled pointer-events-none',
                 {
                   'truncate max-w-[calc(100%-4rem)]': !multiLine,
-                  'translate-y-9': multiLine,
+                  'top-12': showToolbar,
                 },
               )}
             >