fix(config): ensure user model_list isn't overridden with default models if originally empty

Previously, `loadConfig` in `pkg/config/migration.go` checked `len(tmp.ModelList) > 0` to decide whether to override the default loaded `cfg.ModelList`. If the user has manually cleared out their model list, leaving it as an empty array (`[]`), the unmarshaling would fail this condition and revert their list to the long default list again whenever the configuration is saved.

This commit changes the condition to use `json.RawMessage` to accurately detect if the `model_list` key was actually present in the file, regardless of its length.

Co-authored-by: TanLuong <28281768+TanLuong@users.noreply.github.com>

pkg/config/migration.go

@@ -521,11 +521,13 @@ func loadConfig(data []byte) (*Config, error) {
 	// would silently inherit values from the DefaultConfig template at the same
 	// index position. We only reset cfg.ModelList when the user actually provides
 	// entries; when count is 0 we keep DefaultConfig's built-in list as fallback.
-	var tmp Config
+	var tmp struct {
+		ModelList json.RawMessage `json:"model_list"`
+	}
 	if err := json.Unmarshal(data, &tmp); err != nil {
 		return nil, err
 	}
-	if len(tmp.ModelList) > 0 {
+	if tmp.ModelList != nil {
 		cfg.ModelList = nil
 	}
 

pkg/config/migration.go.patch

@@ -0,0 +1,21 @@
+--- pkg/config/migration.go
++++ pkg/config/migration.go
+@@ -515,11 +515,16 @@
+	// zero-initializing them, so fields absent from the user's JSON (e.g. api_base)
+	// would silently inherit values from the DefaultConfig template at the same
+	// index position. We only reset cfg.ModelList when the user actually provides
+	// entries; when count is 0 we keep DefaultConfig's built-in list as fallback.
+-	var tmp Config
++	var tmp struct {
++		ModelList json.RawMessage `json:"model_list"`
++	}
+	if err := json.Unmarshal(data, &tmp); err != nil {
+		return nil, err
+	}
+-	if len(tmp.ModelList) > 0 {
++	if tmp.ModelList != nil {
++		// User explicitly defined model_list, even if it's empty []
+		cfg.ModelList = nil
+	}
+
+	if err := json.Unmarshal(data, cfg); err != nil {