Autocomplete dropdown closes when pressing arrow keys

### 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

macOS 26.2.0 (25C56)

### Expected behaviour

The cursor should move down within the dropdown to select the next suggestion.

### Actual behaviour

The suggestion dropdown closes when the down arrow key is pressed, preventing branch selection.

### Steps to reproduce

1. Type `git branch -D` (or any command with autocomplete suggestions)
2. The dropdown shows local branches as suggestions
3. Press the down arrow key to navigate through the suggestions

---

## Additional description
I have been using this autocomplete feature since Fig and have continuously upgraded through Q CLI to the current Kiro CLI. However, after the migration to Kiro CLI, the behavior has become problematic.

**Troubleshooting Attempts:**

- Ran `kiro-cli doctor` - no issues detected
- Ran `q doctor` - no issues detected
- Reinstalled kiro-cli - issue persists

**Suspicion:**
Configuration conflicts from the fig → Q CLI → Kiro CLI migration pipeline, though I've found no concrete evidence.

### Environment

```yaml

[q-details]
version = "1.23.0"
hash = "e6c9813d5497e3e0cd679870dc565bd96a29a300"
date = "2025-12-18T22:56:01.616843Z (6h ago)"
variant = "full"

[system-info]
os = "macOS 26.2.0 (25C56)"
chip = "Apple M4"
total-cores = 10
memory = "32.00 GB"

[environment]
cwd = "/Users/USER"
cli-path = "/Users/USER"
os = "Mac"
shell-path = "/bin/zsh"
shell-version = "5.9"
terminal = "iTerm 2"
install-method = "unknown"

[env-vars]
PATH = "/Users/USER/.antigravity/antigravity/bin:/Users/USER/.local/share/claude/versions:/opt/homebrew/opt/curl/bin:/Users/USER/.volta/bin:/Users/USER/.docker/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/pmk/env/global/bin:/Applications/iTerm.app/Contents/Resources/utilities:/Users/USER/.local/bin"
QTERM_SESSION_ID = "d0248a287b7c46bd904e70f19b3357d6"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.23.0"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.googlecode.iterm2"
```