Regression: exit summary not shown after upgrading to 1.0.74 / 1.0.75

## Summary
After upgrading from `1.0.73` to `1.0.74` (and still broken in `1.0.75`), the CLI no longer prints the session/exit summary when quitting. Rolling back to `1.0.73` restores the expected behavior.

## Environment
- Copilot CLI: broken on `1.0.74` and `1.0.75`; works on `1.0.73` (current rollback)
- OS: Ubuntu 22.04.5 LTS on WSL2 (kernel `6.18.33.1-microsoft-standard-WSL2`)
- Terminal: `xterm-256color`
- Shell: `/bin/bash`
- `TERM=xterm-256color`

## Steps to reproduce
1. Run `copilot` (interactive mode).
2. Have a normal conversation.
3. Exit via `/exit` (also tried `ctrl+d`).
4. Observe: no summary is printed on exit.

## Expected behavior
On exit, the CLI prints a session summary (as it does in `1.0.73`).

## Notes
- `/exit print` still force-prints the session content, but the normal automatic summary on exit is missing.
- Verified on both `1.0.74` and `1.0.75` before rolling back to `1.0.73`.
- No relevant setting in `settings.json` appears to gate this (`showTimestamps`, footer settings, etc. were checked).

## Regression range
First bad: `1.0.74` — Last good: `1.0.73`

运行交互式 copilot CLI 并使用 /exit 或 ctrl+d 退出，以重现回归，然后比较 1.0.73 和 1.0.74 之间的行为。跟踪正常退出路径，而不是用于打印的 /exit 命令；当退出时返回自动会话摘要且不破坏现有的强制打印行为时，即表示完成。

由索引模型根据 Issue 内容生成。