Add formatters module

src/contextgen/formatters/json_formatter.py

@@ -0,0 +1,23 @@
+"""JSON formatter for structured output."""
+
+import json
+from pathlib import Path
+from typing import Any
+
+
+class JSONFormatter:
+    """Formats context data as JSON."""
+
+    def __init__(self, output_path: Path | None = None):
+        self.output_path = output_path
+
+    def format(self, data: dict[str, Any]) -> str:
+        """Format data as JSON string."""
+        return json.dumps(data, indent=2, ensure_ascii=False)
+
+    def save(self, data: dict[str, Any]) -> None:
+        """Save formatted data to file."""
+        if self.output_path:
+            self.output_path.parent.mkdir(parents=True, exist_ok=True)
+            content = self.format(data)
+            self.output_path.write_text(content, encoding="utf-8")