🐛 | Improve test coverage for SonarQube quality gate

- Restructure conftest to try real Qt first, fall back to stubs
  only if that fails — ensures try/except guards in player.py and
  gui.py are exercised in CI, improving new_coverage
- Add tests for _migrate_legacy error paths (JSONDecodeError,
  OSError, db migration) — config.py now 100% covered
- Add tests for _disconnect, _send_presence exception handlers —
  discord_rpc.py now 97% covered
- Add tests for _cleanup_path and _tmp_dir helpers — player.py
  coverage bumped to 33%

tests/test_config.py

@@ -59,6 +59,10 @@ class TestLoadConfig:
         assert loaded["volume"] == 50  # default
         # The corrupt file is not overwritten, but defaults are returned
 
+
+class TestMigrateLegacy:
+    """Tests for the legacy config migration path."""
+
     def test_legacy_migration(self, _patch_config_paths):
         """Legacy config in project dir is migrated to XDG location."""
         cfg = _patch_config_paths
@@ -76,8 +80,63 @@ class TestLoadConfig:
         assert not cfg._LEGACY_FILE.exists()
         assert cfg._LEGACY_FILE.with_suffix(".json.migrated").exists()
 
+    def test_legacy_migration_corrupt_json_ignored(self, _patch_config_paths):
+        """Corrupt legacy JSON is silently ignored (covers JSONDecodeError)."""
+        cfg = _patch_config_paths
+        cfg.CONFIG_FILE.unlink(missing_ok=True)
+        cfg.SETTINGS = dict(cfg.DEFAULT_CONFIG)
+
+        cfg._LEGACY_FILE.write_text("not valid json at all")
+        loaded = cfg.load_config()  # should not crash
+        assert loaded["volume"] == 50  # defaults returned
+
+    def test_legacy_oserror_handled_gracefully(self, _patch_config_paths, monkeypatch):
+        """OSError during migration is silently ignored."""
+        cfg = _patch_config_paths
+        cfg.CONFIG_FILE.unlink(missing_ok=True)
+        cfg.SETTINGS = dict(cfg.DEFAULT_CONFIG)
+
+        cfg._LEGACY_FILE.write_text(json.dumps({"volume": 80}))
+
+        # Make ``os.rename`` fail (used by Path.rename)
+        def _fail_rename(src, dst):
+            raise OSError("Permission denied")
+
+        monkeypatch.setattr(os, "rename", _fail_rename)
+
+        # load_config should catch the OSError
+        loaded = cfg.load_config()
+        # save_config runs BEFORE the failing rename, so the value IS persisted
+        assert loaded["volume"] == 80
+
+    def test_legacy_db_migration(self, _patch_config_paths):
+        """Database file from legacy project dir is copied to XDG location."""
+        cfg = _patch_config_paths
+        cfg.CONFIG_FILE.unlink(missing_ok=True)
+        cfg.SETTINGS = dict(cfg.DEFAULT_CONFIG)
+
+        # The migration only copies the db if old_db_path.parent matches
+        # the config.py directory. Create the legacy db there.
+        config_dir = Path(cfg.__file__).parent
+        legacy_db = config_dir / "music_history.db"
+        legacy_db.write_text("fake db content")
+
+        legacy = {**cfg.DEFAULT_CONFIG, "db_path": str(legacy_db)}
+        cfg._LEGACY_FILE.write_text(json.dumps(legacy))
+
+        loaded = cfg.load_config()
+        # db_path should point to the new XDG location
+        assert loaded["db_path"] == str(cfg.CONFIG_DIR / "music_history.db")
+        assert cfg.CONFIG_DIR.exists()
+        # Original file should still exist
+        assert legacy_db.exists()
+
+        # Clean up
+        legacy_db.unlink(missing_ok=True)
+
 
 class TestSaveConfig:
+
     def test_save_config_persists(self, _patch_config_paths):
         """save_config writes merged config to disk."""
         cfg = _patch_config_paths