feat: scaffold stentor-gateway with FastAPI voice pipeline

Initialize the stentor-gateway project with WebSocket-based voice
pipeline orchestrating STT → Agent → TTS via OpenAI-compatible APIs.

- Add FastAPI app with WebSocket endpoint for audio streaming
- Add pipeline orchestration (stt_client, tts_client, agent_client)
- Add Pydantic Settings configuration and message models
- Add audio utilities for PCM/WAV conversion and resampling
- Add health check endpoints
- Add Dockerfile and pyproject.toml with dependencies
- Add initial test suite (pipeline, STT, TTS, WebSocket)
- Add comprehensive README covering gateway and ESP32 ear design
- Clean up .gitignore for Python/uv project

stentor-gateway/tests/test_stt_client.py

@@ -0,0 +1,89 @@
+"""Tests for the Speaches STT client."""
+
+import httpx
+import pytest
+
+from stentor.audio import pcm_to_wav
+from stentor.stt_client import STTClient
+
+
+class TestSTTClient:
+    """Tests for STTClient."""
+
+    @pytest.fixture
+    def stt_client(self, settings):
+        """Create an STT client with a mock HTTP client."""
+        http_client = httpx.AsyncClient()
+        return STTClient(settings, http_client)
+
+    async def test_transcribe_success(self, settings, sample_pcm, httpx_mock):
+        """Test successful transcription."""
+        httpx_mock.add_response(
+            url=f"{settings.stt_url}/v1/audio/transcriptions",
+            method="POST",
+            json={"text": "Hello world"},
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = STTClient(settings, http_client)
+            wav_data = pcm_to_wav(sample_pcm)
+            result = await client.transcribe(wav_data)
+
+        assert result == "Hello world"
+
+    async def test_transcribe_with_language(self, settings, sample_pcm, httpx_mock):
+        """Test transcription with explicit language."""
+        httpx_mock.add_response(
+            url=f"{settings.stt_url}/v1/audio/transcriptions",
+            method="POST",
+            json={"text": "Bonjour le monde"},
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = STTClient(settings, http_client)
+            wav_data = pcm_to_wav(sample_pcm)
+            result = await client.transcribe(wav_data, language="fr")
+
+        assert result == "Bonjour le monde"
+
+    async def test_transcribe_empty_result(self, settings, sample_pcm, httpx_mock):
+        """Test transcription returning empty text."""
+        httpx_mock.add_response(
+            url=f"{settings.stt_url}/v1/audio/transcriptions",
+            method="POST",
+            json={"text": "  "},
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = STTClient(settings, http_client)
+            wav_data = pcm_to_wav(sample_pcm)
+            result = await client.transcribe(wav_data)
+
+        assert result == ""
+
+    async def test_is_available_success(self, settings, httpx_mock):
+        """Test availability check when service is up."""
+        httpx_mock.add_response(
+            url=f"{settings.stt_url}/v1/models",
+            method="GET",
+            json={"models": []},
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = STTClient(settings, http_client)
+            available = await client.is_available()
+
+        assert available is True
+
+    async def test_is_available_failure(self, settings, httpx_mock):
+        """Test availability check when service is down."""
+        httpx_mock.add_exception(
+            httpx.ConnectError("Connection refused"),
+            url=f"{settings.stt_url}/v1/models",
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = STTClient(settings, http_client)
+            available = await client.is_available()
+
+        assert available is False