Add test.py with addition function

Add a simple Python function that adds two numbers.
Includes example usage when run as main.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

test.py

@@ -0,0 +1,9 @@
+def add_numbers(a, b):
+    """Return the sum of two numbers."""
+    return a + b
+
+
+if __name__ == "__main__":
+    # Example usage
+    result = add_numbers(5, 3)
+    print(f"5 + 3 = {result}")