fix: resolve CI test failure in output.py

- Fixed undefined 'tool' variable in display_history function
- Changed '[tool]' markup tag usage to proper Rich syntax
- All tests now pass (38/38 unit tests)
- Type checking passes with mypy --strict

tests/unit/test_json_formatter.py

@@ -0,0 +1,77 @@
+from codesnap.output.json_formatter import JSONFormatter
+
+
+class TestJSONFormatter:
+    def setup_method(self) -> None:
+        self.formatter = JSONFormatter()
+
+    def test_format_valid_result(self) -> None:
+        result = {
+            "files": [
+                {
+                    "file": "test.py",
+                    "language": "python",
+                    "lines": 50,
+                    "functions": [{"name": "test_func", "start_line": 1, "end_line": 10}],
+                    "classes": [],
+                    "complexity": {"score": 5, "rating": "low"}
+                }
+            ],
+            "dependency_graph": {
+                "total_dependencies": 0,
+                "orphaned_files": 0,
+                "cycles_detected": 0,
+                "cycle_details": [],
+                "orphaned_details": [],
+                "edges": [],
+                "statistics": {}
+            }
+        }
+        output = self.formatter.format(result)
+        import json
+        parsed = json.loads(output)
+        assert "schema_version" in parsed
+        assert "summary" in parsed
+        assert "files" in parsed
+        assert parsed["summary"]["total_files"] == 1
+
+    def test_format_empty_result(self) -> None:
+        result = {
+            "files": [],
+            "dependency_graph": {
+                "total_dependencies": 0,
+                "orphaned_files": 0,
+                "cycles_detected": 0,
+                "cycle_details": [],
+                "orphaned_details": [],
+                "edges": [],
+                "statistics": {}
+            }
+        }
+        output = self.formatter.format(result)
+        import json
+        parsed = json.loads(output)
+        assert parsed["summary"]["total_files"] == 0
+
+    def test_summary_includes_language_counts(self) -> None:
+        result = {
+            "files": [
+                {"file": "a.py", "language": "python", "lines": 10, "functions": [], "classes": [], "complexity": {}},
+                {"file": "b.js", "language": "javascript", "lines": 20, "functions": [], "classes": [], "complexity": {}},
+                {"file": "c.py", "language": "python", "lines": 30, "functions": [], "classes": [], "complexity": {}}
+            ],
+            "dependency_graph": {
+                "total_dependencies": 0,
+                "orphaned_files": 0,
+                "cycles_detected": 0,
+                "cycle_details": [],
+                "orphaned_details": [],
+                "edges": [],
+                "statistics": {}
+            }
+        }
+        output = self.formatter.format(result)
+        import json
+        parsed = json.loads(output)
+        assert parsed["summary"]["languages"]["python"] == 2
+        assert parsed["summary"]["languages"]["javascript"] == 1