feat: Support custom default agent
Fix https://github.com/sst/opencode/issues/4443.
This pr is intend to replace https://github.com/sst/opencode/pull/4447 since it seems buggy.
@rekram1-node I added a default_agent field in config, and a default field in Agent.Info to indicate if an agent is assigned to default. Some related logic in TUI and ACP had been updated. If I missed anything pls let me know.
thanks! ill have to give it a test
/review
/review
lgtm
Wait I found several places (e.g. desktop app) need to be updated
@rekram1-node I think we are ready here