I have to restart q to use a different agent/profile

### 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 15.5.0 (24F74)

### Expected behaviour

switch your agent by doing /agent use X or just /agent and then choosing the agent like with /model command,

### Actual behaviour

I also have to set the profile or agent I want to use as a default and restart the q chat tool losing context, a bit frustrating experience

### Steps to reproduce

_No response_

### Environment

```yaml

[q-details]
version = "1.13.0"
hash = "7dee6efdf68f6343e80a56028e6b40f8eff77746"
date = "2025-07-31T02:57:26.581678Z (2d ago)"

[system-info]
os = "macOS 15.5.0 (24F74)"
chip = "Apple M1 Pro"
total-cores = 10
memory = "32.00 GB"

[environment]
cwd = "/Users/USER/data"
cli-path = "/Users/USER/data"
install-method = "unknown"

[env-vars]
PATH = "omitted"
QTERM_SESSION_ID = "b97d264c2c8a467690c1a09221af0703"
Q_SET_PARENT_CHECK = "1"
Q_TERM = "1.12.7"
Q_USING_ZSH_AUTOSUGGESTIONS = "1"
SHELL = "/bin/zsh"
TERM = "xterm-256color"
__CFBundleIdentifier = "com.googlecode.iterm2"
```

Inizia riproducendo il comportamento in un terminal macOS con q 1.13.0: usa /agent o /agent use X, quindi confronta il passaggio da un profilo o agente all’altro con e senza q restart. È completato quando la modifica dell’agente o del profilo attivo funziona nella sessione di chat esistente senza impostare un valore predefinito né perdere il contesto.

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