Qwen Coder oAuth support

[konard]

We need to research CLI agentic tools like

claude
opencode
gemini
qwen

And propose all possible ways to implement oAuth workflow in our agent specifically for Qwen Coder model. So we do use the same oAuth (login flow as in Qwen Coder CLI).

We should also be compatible with oAuth data stored by Qwen Code CLI, so if it gone through the auth, we will be automatically just use it.

Also if no Qwen Code CLI oAuth data was found we should just use .agent/qwen folder (or what ever we use for our app folder in unix).

As for the our agent CLI I need to carefully consider all possible ways for user to login via our agent CLI. So we need to investigate how other tools do it, and propose variants for all steps in the flow.