Add contributor guide and project usage docs

tests/test_pty_manager.py

@@ -0,0 +1,16 @@
+"""PtyManager 테스트."""
+
+from lazy_enter.pty_manager import PtyManager
+
+
+def test_initial_state():
+    pty = PtyManager("echo hello")
+    assert not pty.is_alive
+
+
+def test_start_and_stop():
+    pty = PtyManager("cat")
+    pty.start()
+    assert pty.is_alive
+    pty.stop()
+    assert not pty.is_alive