One-Shot model change

### Describe the feature or problem you'd like to solve

Sometimes you want to use a more advanced model for a bigger query, or a simpler model for a faster query. Currently you have to switch the model and switch back

### Proposed solution

Either Expand `/model` to receive an optional command argument, or introduce a `/with-model` command, to run a prompt with a specific model

### Example prompts or workflows

`/model claude-haiku-4.5 sync git to server`

### Additional context

_No response_