fix: remaining lint issues (golines, godoclint)

- QQConfig: match upstream struct formatting exactly (golines)
- model_resolution.go: remove package godoc (godoclint), add nolint:unused

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pkg/agent/model_resolution.go

@@ -1,6 +1,3 @@
-// model_resolution.go provides model-list resolution helpers used by the upstream
-// loop refactor. These functions are currently unused but will be wired in PR4
-// (upstream-merge/core-loop).
 package agent
 
 import (