refactor(playground): extract input submit text helper

- move prompt submit text validation into input control utilities
- let the input component submit only when a concrete text value is available

web/default/src/features/playground/components/playground-input.tsx

@@ -24,6 +24,7 @@ import {
   PromptInputTextarea,
   type PromptInputMessage,
 } from '@/components/ai-elements/prompt-input'
+import { getSubmittableInputText } from '../lib'
 import type { ModelOption, GroupOption } from '../types'
 import { PlaygroundInputControls } from './playground-input-controls'
 import { PlaygroundInputTools } from './playground-input-tools'
@@ -60,8 +61,10 @@ export function PlaygroundInput({
   const [text, setText] = useState('')
 
   const handleSubmit = (message: PromptInputMessage) => {
-    if (!message.text?.trim() || disabled) return
-    onSubmit(message.text)
+    const submittableText = getSubmittableInputText(message, disabled)
+
+    if (!submittableText) return
+    onSubmit(submittableText)
     setText('')
   }
 

web/default/src/features/playground/lib/input-control-utils.ts

@@ -34,6 +34,21 @@ type InputControlState = {
   shouldShowStop: boolean
 }
 
+type SubmittableInputMessage = {
+  text?: string | null
+}
+
+export function getSubmittableInputText(
+  message: SubmittableInputMessage,
+  disabled?: boolean
+): string | null {
+  if (disabled || !message.text?.trim()) {
+    return null
+  }
+
+  return message.text
+}
+
 export function getInputControlState({
   disabled,
   groups,