Refactor code structure for improved readability and maintainability

tests/test_runtime.py

@@ -4,7 +4,7 @@ from pathlib import Path
 
 import pytest
 
-from yt_shorts_downloader import runtime
+from yt_shorts_downloader.core import runtime
 
 
 def test_find_supported_js_runtimes_prefers_deno(
@@ -37,9 +37,7 @@ def test_find_supported_js_runtimes_uses_best_supported_node(
     monkeypatch.setattr(
         runtime,
         "_probe_executable_version",
-        lambda executable: (22, 9, 0)
-        if executable.endswith("v22.9.0/bin/node")
-        else (22, 1, 0),
+        lambda executable: (22, 9, 0) if executable.endswith("v22.9.0/bin/node") else (22, 1, 0),
     )
 
     runtimes = runtime.find_supported_js_runtimes()