kiro-cli translate returns "no valid completions were generated" on Amazon Linux 2023

### Description

`kiro-cli translate` fails on Amazon Linux 2023 (x86_64) with "no valid completions were generated" while the same command works on macOS. The API call succeeds (HTTP 200, returns a request_id) but the response contains no completions.

### Steps to Reproduce

1. Install kiro-cli on an Amazon Linux 2023 instance
2. Run `kiro-cli setup` and `kiro-cli login`
3. Verify `kiro-cli doctor` passes all checks
4. Run `kiro-cli translate "How much space do I have left on my home partition?"`

**Expected**: A shell command suggestion (e.g. `df -h ~`)
**Actual**: `error: no valid completions were generated`

### Works on macOS

Same command on macOS (same kiro-cli version 1.29.7) correctly generates:
```bash
df -h ~ | awk '{print $4}'
```

### Verbose output shows

Running with `-vvv`, the API call completes successfully (Cognito auth ✓, CodeWhisperer generateCompletions returns HTTP 200 with request_id) but the deserialized response has no valid completions. Error originates at `crates/q_cli/src/cli/translate.rs:436`.

### Environment

**Amazon Linux (FAILS):**
- kiro-cli version: 1.29.7
- OS: Amazon Linux 2023.11.20260406
- Kernel: 6.12.73-95.123.amzn2023.x86_64
- Shell: zsh
- kiro-cli doctor: all checks pass ✔

**macOS (WORKS):**
- kiro-cli version: 1.29.7
- OS: macOS Tahoe 26.4 (Build 25E246)
- Shell: zsh
- kiro-cli translate generates correct output