feat(arena): improve cancellation handling and simplify to in-process mode

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

- Track user-initiated cancellation separately from failures

- Cancel round immediately when user denies a tool call

- Add message queue to handle input during streaming

- Add info messages during Arena operations (apply, stop, cleanup)

- Disable tmux/iTerm2 backends (only in-process mode supported)

- Polish UI: green tool count, updated warning prefix

This improves the Arena UX by providing clearer feedback and

properly handling user cancellations without treating them as failures.

packages/cli/src/ui/components/messages/StatusMessages.tsx

@@ -75,7 +75,7 @@ export const SuccessMessage: React.FC<StatusTextProps> = ({ text }) => (
 export const WarningMessage: React.FC<StatusTextProps> = ({ text }) => (
   <StatusMessage
     text={text}
-    prefix="⚠"
+    prefix="△"
     prefixColor={theme.status.warning}
     textColor={theme.status.warning}
   />