feat: define transcription service boundary

src/voice_transcriptor/services/transcription.py

@@ -0,0 +1,13 @@
+from voice_transcriptor.models import AppSettings, MediaInfo
+
+
+class TranscriptionNotImplementedError(RuntimeError):
+    """Raised because transcription is outside the milestone 1 scope."""
+
+
+class TranscriptionService:
+    def transcribe(self, media: MediaInfo, settings: AppSettings) -> None:
+        del media, settings
+        raise TranscriptionNotImplementedError(
+            "Transcription is not implemented in milestone 1."
+        )

tests/test_transcription.py

@@ -0,0 +1,26 @@
+from pathlib import Path
+
+import pytest
+
+from voice_transcriptor.models import AppSettings, MediaInfo
+from voice_transcriptor.services.transcription import (
+    TranscriptionNotImplementedError,
+    TranscriptionService,
+)
+
+
+def test_transcribe_raises_milestone_exception_with_user_readable_message() -> None:
+    media = MediaInfo(
+        path=Path("sample.mp3"),
+        size_bytes=1,
+        duration_seconds=1.0,
+        audio_codec="mp3",
+    )
+    settings = AppSettings(
+        model="gpt-4o-mini-transcribe",
+        language="en",
+        output_directory=Path("output"),
+    )
+
+    with pytest.raises(TranscriptionNotImplementedError, match="(?i)not implemented"):
+        TranscriptionService().transcribe(media, settings)