tests: add chat model tests(cv: 100)

test/dashbot/models/dashbot_window_model_test.dart

@@ -0,0 +1,58 @@
+import 'package:apidash/dashbot/core/model/dashbot_window_model.dart';
+import 'package:test/test.dart';
+
+void main() {
+  group('DashbotWindowModel', () {
+    test('default values', () {
+      const model = DashbotWindowModel();
+      expect(model.width, 400);
+      expect(model.height, 515);
+      expect(model.right, 50);
+      expect(model.bottom, 100);
+      expect(model.isActive, false);
+      expect(model.isPopped, true);
+      expect(model.isHidden, false);
+    });
+
+    test('copyWith changes only specified fields', () {
+      const original = DashbotWindowModel();
+      final updated = original.copyWith(
+        width: 420,
+        height: 600,
+        isActive: true,
+        isHidden: true,
+      );
+
+      expect(updated.width, 420);
+      expect(updated.height, 600);
+      expect(updated.isActive, true);
+      expect(updated.isHidden, true);
+
+      // Unchanged fields retain original values
+      expect(updated.right, original.right);
+      expect(updated.bottom, original.bottom);
+      expect(updated.isPopped, original.isPopped);
+
+      // Original remains unchanged
+      expect(original.width, 400);
+      expect(original.height, 515);
+      expect(original.isActive, false);
+      expect(original.isHidden, false);
+    });
+
+    test('copyWith chaining', () {
+      const original = DashbotWindowModel();
+      final chained = original
+          .copyWith(width: 410)
+          .copyWith(right: 80, bottom: 120)
+          .copyWith(isPopped: false);
+
+      expect(chained.width, 410);
+      expect(chained.right, 80);
+      expect(chained.bottom, 120);
+      expect(chained.isPopped, false);
+      // untouched
+      expect(chained.height, original.height);
+    });
+  });
+}