kiro-cli not updating since version 2.19.0

### Checks

- [x] I have searched [github.com/aws/amazon-q-developer-cli/issues](https://github.com/aws/amazon-q-developer-cli/issues?q=) and there are no duplicates of my issue
- [x] I have run `q doctor` in the affected terminal session
- [x] I have run `q restart` and replicated the issue again

### Operating system

Linux 7.0.0-1011-aws - Ubuntu 26.04 LTS

### Expected behaviour

kiro-cli must update as soon there is one available.

### Actual behaviour

kiro-cli ceased to update. Below is the error that occurs in the end of update process:

$ kiro-cli update
████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████ 100/100error: failed to unpack `/tmp/.tmpCrmUAf/kirocli/bin/kiro-cli-chat`

If this is unexpected, try running kiro-cli doctor and then try again.

### Steps to reproduce

$ kiro-cli update
████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████████ 100/100error: failed to unpack `/tmp/.tmpCrmUAf/kirocli/bin/kiro-cli-chat`

If this is unexpected, try running kiro-cli doctor and then try again.

$ kiro-cli doctor

✔ Everything looks good!

Kiro CLI still not working? Run kiro-cli issue to let us know!

### Environment

```yaml

[q-details]
version = "2.19.0"
hash = "60eb656b3201c6e0a5b800c3b9dde677e0e33396"
date = "2026-08-19T22:22:48.411638Z (9d ago)"
variant = "minimal"

[system-info]
chip = "Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz"
total-cores = 2
memory = "3.82 GB"

[system-info.os.linux]
kernel_version = "7.0.0-1011-aws"
id = "ubuntu"
name = "Ubuntu"
pretty_name = "Ubuntu 26.04 LTS"
version_id = "26.04"
version = "26.04 LTS (Resolute Raccoon)"

[environment]
cwd = "/home/USER/Documents/prj002_altcoin_screener"
cli-path = "/home/USER/Documents/prj002_altcoin_screener"
os = "Linux"
shell-path = "/usr/bin/bash"
shell-version = "5.3.9"
install-method = "unknown"
in-ssh = true

[env-vars]
PATH = "/home/USER/.npm-global/bin:/home/USER/.local/bin:/home/USER/.npm-global/bin:/home/USER/anaconda3/bin:/home/USER/anaconda3/condabin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:/usr/local/games:/snap/bin:/home/USER/.local/bin"
QTERM_SESSION_ID = "ce601a6bbc6644df8eb5478e639e8362"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "2.19.0"
SHELL = "/bin/bash"
TERM = "xterm-256color"
XDG_SESSION_TYPE = "tty"
```

まず、報告された Linux 環境で `kiro-cli update` を再現し、`kiro-cli-chat` の展開を処理する updater のパスを調査します。更新の失敗を、成功した `kiro-cli doctor` の出力および既存の updater テスト（利用可能な場合）と比較します。バージョン 2.19.0 からの更新が展開エラーなしで完了し、インストール済みの CLI が新しいバージョンになることを完了条件とします。

索引モデルが issue の本文から書いたものです。