Refactor test configurations and enhance testing framework

- Replace TempConfig with DummyConfig across tests for consistency
- Introduce unit tests workflow configuration
- Add pytest configuration for standardized test discovery
- Implement comprehensive tests for config loading and downloader behavior
- Clean up unused temp_config.py and related references

tests/test_playlist_manager_run_behaviour.py

@@ -0,0 +1,23 @@
+import logging
+from ytplaylist.manager import PlaylistManager
+from tests.dummy_config import DummyConfig
+
+
+def test_run_with_prune_disabled():
+    logging.basicConfig(level=logging.INFO, format="%(levelname)s:%(message)s")
+    cfg = DummyConfig()
+    cfg.playlists = [{"url": None, "save_path": "tests/tmp_test", "archive": "archive.txt"}]
+    m = PlaylistManager(cfg, debug=False)
+    # should complete without raising
+    m.run()
+
+
+def test_run_with_prune_enabled_non_interactive():
+    logging.basicConfig(level=logging.INFO, format="%(levelname)s:%(message)s")
+    cfg = DummyConfig()
+    cfg.playlists = [{"url": None, "save_path": "tests/tmp_test", "archive": "archive.txt"}]
+    cfg.prune = True
+    cfg.non_interactive = True
+    m = PlaylistManager(cfg, debug=False)
+    # should complete without raising
+    m.run()