File deletion update

### 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 15.3.2 (24D81)

### Expected behaviour

When we request test case generation, the system should preserve existing user-written test cases (or make only minor changes to them) while generating additional test cases. Similarly, when we request new features, the system should preserve the current implementation while adding the necessary code to implement the requested functionality.

### Actual behaviour

Q was removing a significant portion (approximately half) of user-written test cases.

### Steps to reproduce

Clone any repository that contains test cases, then request the system to generate additional test cases for that repository.

### Environment

```yaml

[q-details]
version = "1.7.3"
hash = "3e4ae79d371315e80ddac772b43fff2cba314104"
date = "2025-04-10T05:48:16.435186Z (5d ago)"
variant = "full"

[system-info]
os = "macOS 15.3.2 (24D81)"
chip = "Apple M3 Pro"
total-cores = 12
memory = "36.00 GB"

[environment]
cwd = "/Users/USER/GitHub/AgenticQChat/QDeveloperMaestroPythonSidecar"
cli-path = "/Users/USER/GitHub/AgenticQChat/QDeveloperMaestroPythonSidecar"
os = "Mac"
shell-path = "/opt/homebrew/Cellar/zsh/5.9/bin/zsh"
shell-version = "5.9"
terminal = "VSCode"
install-method = "unknown"

[env-vars]
PATH = "/Users/USER/GitHub/AgenticQChat/.venv/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:/Users/USER/.vscode/extensions/ms-python.python-2025.4.0-darwin-arm64/python_files/deactivate/zsh:/Users/USER/GitHub/AgenticQChat/.venv/bin:/Users/USER/.local/bin:/Users/USER/.toolbox/bin:/Users/USER/.toolbox/bin"
QTERM_SESSION_ID = "7dde80227e4149b8a299289a6346552b"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.7.3"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.microsoft.VSCode"
```

Riproduci il problema con q doctor e q restart in un repository clonato contenente test scritti dall’utente, quindi esamina le modifiche risultanti dopo aver richiesto la generazione di test aggiuntivi. Confronta il diff generato con i test e l’implementazione originali; il lavoro è completato quando il codice utente esistente viene preservato e vengono apportate solo le aggiunte richieste.

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