feat(arena): add IDLE status for agent follow-up task support

- Introduce AgentStatus.IDLE for agents that finished work but can accept follow-up messages
- Add isSettledStatus() helper to check if agent is settled (IDLE or terminal)
- Update ArenaManager to transition to IDLE after agents finish initial task
- Keep agent tabs visible when session is IDLE so users can continue interacting
- Fix listener cleanup to not detach on IDLE (agents remain alive)
- Update tests to expect 'idle' status after successful completion

This enables the arena collaboration feature where agents can receive
additional tasks after completing their initial work.

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

packages/cli/src/ui/components/Composer.tsx

@@ -104,8 +104,8 @@ export const Composer = () => {
 
       {/* Exclusive area: only one component visible at a time */}
       {/* Hide footer when a confirmation dialog (e.g. ask_user_question) is active */}
-      {!showSuggestions &&
-        uiState.streamingState !== StreamingState.WaitingForConfirmation &&
+      {uiState.isInputActive &&
+        !showSuggestions &&
         (showShortcuts ? (
           <KeyboardShortcuts />
         ) : (

packages/cli/src/ui/components/arena/ArenaCards.tsx

@@ -148,11 +148,13 @@ export const ArenaSessionCard: React.FC<ArenaSessionCardProps> = ({
   const colChanges = 10;
 
   const titleLabel =
-    sessionStatus === 'completed'
-      ? 'Arena Complete'
-      : sessionStatus === 'cancelled'
-        ? 'Arena Cancelled'
-        : 'Arena Failed';
+    sessionStatus === 'idle'
+      ? 'Agents Status · Idle'
+      : sessionStatus === 'completed'
+        ? 'Arena Complete'
+        : sessionStatus === 'cancelled'
+          ? 'Arena Cancelled'
+          : 'Arena Failed';
 
   return (
     <Box
@@ -266,6 +268,15 @@ export const ArenaSessionCard: React.FC<ArenaSessionCardProps> = ({
       <Box height={1} />
 
       {/* Hint */}
+      {sessionStatus === 'idle' && (
+        <Box flexDirection="column">
+          <Text color={theme.text.secondary}>
+            Switch to an agent tab to continue, or{' '}
+            <Text color={theme.text.accent}>/arena select</Text> to pick a
+            winner.
+          </Text>
+        </Box>
+      )}
       {sessionStatus === 'completed' && (
         <Box>
           <Text color={theme.text.secondary}>

packages/cli/src/ui/components/arena/ArenaStatusDialog.tsx

@@ -12,7 +12,7 @@ import {
   type ArenaAgentState,
   type InProcessBackend,
   type AgentStatsSummary,
-  isTerminalStatus,
+  isSettledStatus,
   ArenaSessionStatus,
   DISPLAY_MODE,
 } from '@qwen-code/qwen-code-core';
@@ -46,7 +46,7 @@ function pad(
 }
 
 function getElapsedMs(agent: ArenaAgentState): number {
-  if (isTerminalStatus(agent.status)) {
+  if (isSettledStatus(agent.status)) {
     return agent.stats.durationMs;
   }
   return Date.now() - agent.startedAt;
@@ -61,6 +61,8 @@ function getSessionStatusLabel(status: ArenaSessionStatus): {
       return { text: 'Running', color: theme.status.success };
     case ArenaSessionStatus.INITIALIZING:
       return { text: 'Initializing', color: theme.status.warning };
+    case ArenaSessionStatus.IDLE:
+      return { text: 'Idle', color: theme.status.success };
     case ArenaSessionStatus.COMPLETED:
       return { text: 'Completed', color: theme.status.success };
     case ArenaSessionStatus.CANCELLED: