Turn Duo Developer into an actual developer
## Problem
Duo Developer as it stands right now has a very limited feature set: It takes an issue and turns it into an MR. The end user has comparably little influence on how this happens, beyond providing instructions in the issue and Agents.md, and some parts of it are more hard-coded than they might need to be.
While a "mention" trigger can be added to Duo Developer the UX and setup is not optimized for reacting to feedback on the MR it created, which turns it into a "one-shot" approach only.
It is also limited in how much it verifies its own output to make sure it works appropriately.
All of these are severe limitations to Duo Developers usefulness during daily development and limit its ability to deliver a feature end-to-end.
## Desired Outcome
Duo Developer covers the core parts of being a developer teammate, in so far that it:
1. Creates MRs that cover core hygiene (using appropriate templates, adding tests where appropriate etc.)
2. It's code is as likely to pass CI as any developers code
3. Can react to feedback delivered inside the MR to improve it.
epic