Read the eval target model from the user settings scope

Why: The live report's model field came back empty because the settings
endpoint nests models under the user scope ({defaults, project, schema, user}),
not at the top level; the before-baseline report had to be annotated by hand.

Evidence: SELF - vet with -tags live passes; the scope shape verified against
GET /api/settings on the qa instance.

Impact: Future live reports carry the served model without manual annotation.

eval/live/live_test.go

@@ -192,15 +192,18 @@ func TestLiveSuite(t *testing.T) {
 		}
 	}
 	c := &client{base: base, http: &http.Client{Timeout: 120 * time.Second}, t: t}
+	// /api/settings 的形状是 {defaults, project, schema, user}；模型播在 user 作用域。
 	var settings struct {
-		Models struct {
-			Chat struct {
-				Model string `json:"model"`
-			} `json:"chat"`
-		} `json:"models"`
+		User struct {
+			Models struct {
+				Chat struct {
+					Model string `json:"model"`
+				} `json:"chat"`
+			} `json:"models"`
+		} `json:"user"`
 	}
 	_ = c.do("GET", "/api/settings", nil, &settings)
-	c.model = settings.Models.Chat.Model
+	c.model = settings.User.Models.Chat.Model
 
 	proj := struct {
 		ID string `json:"id"`