Quickly switch between pre-set model configs

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

Enable rapid model/effort switching for better efficiency

### Proposed solution

As developer I want in many cases to use the strongest model with highest effort level available. However, typing /model, choosing the model with arrows, then choosing the effort level with right left is cumbersome and might cause be to avoid it and therefore not use the right model for the task.

My proposal is to enable mapping keyboard shortcuts to pre-set models and effort so I can quickly switch between them based on the task.
I assume there are other use cases for custom keyboard mapping.

Alternatively, add option to create custom commands, like for example "/cheap" will switch to a pre-set model I choose with pre-set effort level.
Using an approach like "/agent cheap" can work but it changes tools/behavior and not generic enough.

Another option is to create another command (e.g. "/pmodel") which shows a list of 5 pre-set model configurations I can quickly choose by number.

### Example prompts or workflows

_No response_

### Additional context

_No response_

No files, tests, or entry points are named in the issue. Start by locating the existing /model flow and any keyboard-shortcut or custom-command handling. Compare the proposed approaches with current CLI behavior; done should provide a rapid way to switch between pre-set model and effort configurations.

Written by the indexing model from the issue text.