test(cli): ✅ add tests for prune command

add tests for prune command and some code optimization and formatting.

tests/conftest.py

@@ -34,6 +34,17 @@ def tmp_setup_logging(tmp_log_file):
     setup_logging(file_path=tmp_log_file)
 
 
+@pytest.fixture(autouse=True)
+def tmp_cli_logging(monkeypatch, tmp_path):
+    """Keep the CLI callback from writing run logs into the project `output/logs`.
+
+    The callback builds `LOGGING_PATH / <timestamp>.log` on every command call,
+    so `runner.invoke()` would otherwise create a file in the working tree and
+    add two handlers to the root logger for each test.
+    """
+    monkeypatch.setattr("logwatcher.cli.LOGGING_PATH", tmp_path / "logs")
+
+
 @pytest.fixture(name="original_log_dir")
 def original_log_dir_fixture() -> Path:
     """Return log directory containing real logs.