Bundled bun binary requires AVX — TUI silently fails on non-AVX CPUs (Celeron J4125, etc.)

### 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 6.18.36-1-MANJARO - Manjaro Linux

### Expected behaviour

kiro-cli to work

### Actual behaviour

kiro-cli returns to command prompt
kiro-cli --classic works only

### Steps to reproduce

1. open lxterminal
2. kiro-cli

### Environment

```yaml

[q-details]
version = "2.10.0"
hash = "a5da029503141c8033a11d7ee6569583d915cd90"
date = "2026-06-25T20:04:08.842604Z (9d ago)"
variant = "minimal"

[system-info]
chip = "Intel(R) Celeron(R) J4125 CPU @ 2.00GHz"
total-cores = 4
memory = "7.57 GB"

[system-info.os.linux]
kernel_version = "6.18.36-1-MANJARO"
id = "manjaro"
name = "Manjaro Linux"
pretty_name = "Manjaro Linux"
build_id = "rolling"

[environment]
cwd = "/home/USER"
cli-path = "/home/USER"
os = "Linux"
shell-path = "/usr/bin/bash"
shell-version = "5.3.15"
install-method = "unknown"

[env-vars]
DISPLAY = ":0"
PATH = "/home/USER/.local/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/var/lib/snapd/snap/bin:/var/lib/flatpak/exports/bin:/usr/lib/jvm/default/bin:/usr/bin/site_perl:/usr/bin/vendor_perl:/usr/bin/core_perl:/home/USER/.local/share/gem/ruby/3.0.0/bin"
Q_SET_PARENT_CHECK = "1"
SHELL = "/bin/bash"
TERM = "xterm-256color"
XDG_CURRENT_DESKTOP = "LXDE"
XDG_SESSION_TYPE = "x11"
```

Riproduci il problema con `kiro-cli` sul sistema Celeron J4125 segnalato e confrontalo con `kiro-cli --classic`. Traccia come viene selezionato o avviato il binario bun incluso, quindi verifica che la TUI normale funzioni su CPU prive di AVX, preservando il comportamento esistente sulle CPU supportate.

Scritto dal modello di indicizzazione a partire dal testo della issue.