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_config_loader_basic.py

@@ -0,0 +1,30 @@
+import json
+import shutil
+from pathlib import Path
+
+from ytplaylist.config import ConfigLoader
+
+
+def test_config_loader_reads_properties(tmp_path, monkeypatch):
+    # create a minimal config file with known binary names that exist on PATH
+    cfg = {
+        "playlists": [{"url": "https://www.youtube.com/playlist?list=FAKE", "save_path": "./tmp", "archive": "archive.txt"}],
+        "yt_dlp_path": "python",
+        "ffmpeg_path": "python",
+        "aria2c_path": "python",
+        "max_parallel_downloads": 3,
+        "aria2c_connections": 2,
+    }
+
+    p = tmp_path / "yt-playlist-config.json"
+    p.write_text(json.dumps(cfg), encoding="utf-8")
+
+    # Use absolute path so ConfigLoader doesn't try to create ./config
+    loader = ConfigLoader(str(p))
+
+    assert loader.playlists == cfg["playlists"]
+    assert loader.yt_dlp_path == "python"
+    assert loader.ffmpeg_path == "python"
+    assert loader.aria2c_path == "python"
+    assert loader.max_parallel_downloads == 3
+    assert loader.aria2c_connections == 2