[Feature]: Disable oh-my-opencode via cli command

### Prerequisites

- [x] I have searched existing issues and discussions to avoid duplicates
- [x] This feature request is specific to oh-my-opencode (not OpenCode core)
- [x] I have read the [documentation](https://github.com/code-yeongyu/oh-my-opencode#readme)

### Problem Description

Sometimes I would like to disable oh-my-opencode plugin temporarly and not delete it manually from the opencode json config.

### Proposed Solution

/settings -> disable plugin

### Alternatives Considered

_No response_

### Doctor Output (Optional)

```shell

```

### Additional Context

_No response_

### Feature Type

Configuration Option

### Contribution

- [ ] I'm willing to submit a PR for this feature
- [ ] I can help with testing
- [ ] I can help with documentation