Missing /hook --enable/--disable commands in new agent system

### 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

Prior the agent config files, users were able to dynamically enable/disable hooks during a chat session using commands like `/hook myHook --disable` and `/hook myHook --enable`

### Actual behaviour

The new agent configuration system only supports static hook definitions in JSON files. There are no interactive slash commands to toggle hooks on/off during a session. Users must edit the agent JSON configuration and restart to change hook behavior.

### Steps to reproduce

1. Start a chat session with an agent that has hooks defined
2. Try to use `/hook myHook --disable` command
3. Command is not recognized
4. Check available slash commands - no hook management commands exist
5. Only way to disable hooks is to edit the agent JSON configuration file

### Environment

```yaml

```