fix(test): add skip marker for transcription tests requiring faster_whisper

TestTranscribeLocalExtended patches faster_whisper.WhisperModel, which
triggers an ImportError when the faster_whisper package is not installed.
Added a pytest.mark.skipif marker using importlib.util.find_spec so
these tests are gracefully skipped instead of failing with
ModuleNotFoundError.

tests/tools/test_transcription_tools.py

@@ -414,6 +414,10 @@ class TestTranscribeLocalCommand:
 # _transcribe_local — additional tests
 # ============================================================================
 
+@pytest.mark.skipif(
+    not __import__("importlib").util.find_spec("faster_whisper"),
+    reason="faster_whisper not installed",
+)
 class TestTranscribeLocalExtended:
     def test_model_reuse_on_second_call(self, tmp_path):
         """Second call with same model should NOT reload the model."""