fix(v2): 「移到后台」挪进输入框页脚行（与 Full Auto 双三角同排）

用户反馈浮在输入框上方的大按钮难看。挪进 InputFooter（页脚一行：
Full Auto 三态 · 免责声明 · 移到后台），同一行同一字号同一灰度。
触发条件不变（回合有阻塞中的 shell/subagent 工具时出现，回合
结束自然消失）

Author: lehhair

src/features/chat/ChatPane.tsx

@@ -967,22 +967,6 @@ export const ChatPane = memo(function ChatPane({
       />
 
       <div ref={inputBoxWrapperRef} className="absolute bottom-0 left-0 right-0 z-10 pointer-events-none">
-        {/* 移到后台：shell/task 工具阻塞回合时出现（官方 BackgroundMoveHint
-            同款克制呈现：小号 ghost 文字按钮，不压输入框、不抢眼；
-            回合结束自然消失） */}
-        {blockingBackgroundTasks.length > 0 && (
-          <div className="absolute bottom-full inset-x-0 flex justify-center pb-1.5 z-20">
-            <button
-              type="button"
-              disabled={backgroundMoving}
-              onClick={() => void handleMoveToBackground()}
-              className="pointer-events-auto px-2 py-1 rounded-md text-[length:var(--fs-sm)] text-text-400 hover:text-text-200 hover:bg-bg-200/60 transition-colors disabled:opacity-50"
-              title={blockingBackgroundTasks.map(task => task.label).join('、')}
-            >
-              {t('chat:sessionBackground.move', { count: blockingBackgroundTasks.length })}
-            </button>
-          </div>
-        )}
         {(showCancelHint || (fullAutoHint && !showCancelHint)) && (
           <div className="absolute bottom-full inset-x-0 flex justify-center pb-2 pointer-events-none z-20">
             <div className="px-3 py-1.5 glass border border-border-200/60 rounded-lg shadow-lg text-[length:var(--fs-sm)] text-text-300 animate-in fade-in slide-in-from-bottom-2 duration-150">
@@ -1030,6 +1014,9 @@ export const ChatPane = memo(function ChatPane({
           composerDraft={composerDraft}
           busyDelivery={busyDelivery}
           onBusyDeliveryChange={setBusyDelivery}
+          backgroundTasks={blockingBackgroundTasks}
+          onMoveToBackground={() => void handleMoveToBackground()}
+          backgroundMoving={backgroundMoving}
           canRedo={canRedo}
           revertSteps={redoSteps}
           onRedo={handleRedoWithAnimation}

src/features/chat/InputBox.tsx

@@ -165,6 +165,10 @@ export interface InputBoxProps {
     nonce: number
     restoreStash: boolean
   } | null
+  /** 阻塞中的后台任务（非空时页脚显示「移到后台」入口） */
+  backgroundTasks?: Array<{ label: string }>
+  onMoveToBackground?: () => void
+  backgroundMoving?: boolean
   /** busy 时的投递方式：steer=插队本轮 / queue=排队下轮（流式期间输入栏可切换） */
   busyDelivery?: 'queue' | 'steer'
   onBusyDeliveryChange?: (delivery: 'queue' | 'steer') => void
@@ -217,6 +221,9 @@ function InputBoxComponent({
   composerDraft,
   busyDelivery,
   onBusyDeliveryChange,
+  backgroundTasks,
+  onMoveToBackground,
+  backgroundMoving,
   canRedo = false,
   revertSteps = 0,
   onRedo,
@@ -1622,6 +1629,9 @@ function InputBoxComponent({
             sessionId={sessionId}
             onNewChat={onNewChat}
             inputContainerRef={inputContainerRef}
+            backgroundTasks={backgroundTasks}
+            onMoveToBackground={onMoveToBackground}
+            backgroundMoving={backgroundMoving}
           />
         </div>
       </div>

src/features/chat/input/InputFooter.tsx

@@ -28,9 +28,19 @@ interface InputFooterProps {
   sessionId?: string | null
   onNewChat?: () => void
   inputContainerRef?: RefObject<HTMLDivElement | null>
+  /** 阻塞中的后台任务（非空时显示「移到后台」入口，官方 BackgroundMoveHint 同款克制呈现） */
+  backgroundTasks?: Array<{ label: string }>
+  onMoveToBackground?: () => void
+  backgroundMoving?: boolean
 }
 
-export const InputFooter = memo(function InputFooter({ paneId, onNewChat }: InputFooterProps) {
+export const InputFooter = memo(function InputFooter({
+  paneId,
+  onNewChat,
+  backgroundTasks,
+  onMoveToBackground,
+  backgroundMoving,
+}: InputFooterProps) {
   const { t } = useTranslation(['chat', 'common'])
   const fullAutoMode = useFullAutoMode(paneId)
 
@@ -65,6 +75,21 @@ export const InputFooter = memo(function InputFooter({ paneId, onNewChat }: Inpu
       <button onClick={onNewChat} className="hover:text-text-300 transition-colors">
         {t('inputFooter.pleaseVerify')}
       </button>
+
+      {/* 移到后台（官方 BackgroundMoveHint 同款位置与重量：页脚一行的小字入口） */}
+      {backgroundTasks && backgroundTasks.length > 0 && onMoveToBackground && (
+        <>
+          <span className="text-text-500/30 shrink-0">·</span>
+          <button
+            onClick={onMoveToBackground}
+            disabled={backgroundMoving}
+            className="hover:text-text-300 transition-colors disabled:opacity-50"
+            title={backgroundTasks.map(task => task.label).join('、')}
+          >
+            {t('chat:sessionBackground.move', { count: backgroundTasks.length })}
+          </button>
+        </>
+      )}
     </div>
   )
 })