feat: add microphone field and save_config to Config

tests/test_config.py

@@ -76,3 +76,32 @@ class TestConfigPath:
         from whisper_local.config import _default_config_path
         result = _default_config_path()
         assert result == Path.home() / ".config" / "whisper-local" / "config.toml"
+
+
+class TestMicrophoneConfig:
+    def test_default_microphone_is_empty(self):
+        config = Config()
+        assert config.microphone == ""
+
+    def test_load_device_from_toml(self, tmp_path):
+        config_file = tmp_path / "config.toml"
+        config_file.write_text('[audio]\ndevice = "Headset Mic"\n')
+        config = load_config(config_file)
+        assert config.microphone == "Headset Mic"
+
+
+class TestSaveConfig:
+    def test_save_and_reload(self, tmp_path):
+        from whisper_local.config import save_config
+        path = tmp_path / "config.toml"
+        config = Config(hotkey="KEY_F8", microphone="USB Mic")
+        save_config(config, path)
+        loaded = load_config(path)
+        assert loaded.hotkey == "KEY_F8"
+        assert loaded.microphone == "USB Mic"
+
+    def test_save_creates_parent_dirs(self, tmp_path):
+        from whisper_local.config import save_config
+        path = tmp_path / "subdir" / "config.toml"
+        save_config(Config(), path)
+        assert path.exists()