Support a tiered code-writing system

[yotambarnoy]

In Cursor, even when you select a strong model like Sonnet 4, Cursor minimizes expensive tokens by having Claude do the planning and thinking and laying out the change, and then using a cheaper model for actually processing the change. They then let the superior agent judge if the change was carried out correctly (perhaps by sampling some of the changes) and give it the option to undo the weaker model's work and do the work itself. Obviously this sometimes leads to worse results, but it's a huge money saver.

I would love to duplicate this feature in Roo.