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_tts_client.py

@@ -0,0 +1,78 @@
+"""Tests for the Speaches TTS client."""
+
+import struct
+
+import httpx
+
+from stentor.tts_client import TTSClient
+
+
+class TestTTSClient:
+    """Tests for TTSClient."""
+
+    async def test_synthesize_success(self, settings, httpx_mock):
+        """Test successful TTS synthesis."""
+        # Generate fake PCM audio (100 samples of silence)
+        fake_pcm = struct.pack("<100h", *([0] * 100))
+
+        httpx_mock.add_response(
+            url=f"{settings.tts_url}/v1/audio/speech",
+            method="POST",
+            content=fake_pcm,
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = TTSClient(settings, http_client)
+            result = await client.synthesize("Hello world")
+
+        assert result == fake_pcm
+
+    async def test_synthesize_uses_correct_params(self, settings, httpx_mock):
+        """Test that TTS requests include correct parameters."""
+        httpx_mock.add_response(
+            url=f"{settings.tts_url}/v1/audio/speech",
+            method="POST",
+            content=b"\x00\x00",
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = TTSClient(settings, http_client)
+            await client.synthesize("Test text")
+
+        request = httpx_mock.get_request()
+        assert request is not None
+
+        import json
+        body = json.loads(request.content)
+        assert body["model"] == settings.tts_model
+        assert body["voice"] == settings.tts_voice
+        assert body["input"] == "Test text"
+        assert body["response_format"] == "pcm"
+        assert body["speed"] == 1.0
+
+    async def test_is_available_success(self, settings, httpx_mock):
+        """Test availability check when service is up."""
+        httpx_mock.add_response(
+            url=f"{settings.tts_url}/v1/models",
+            method="GET",
+            json={"models": []},
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = TTSClient(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.tts_url}/v1/models",
+        )
+
+        async with httpx.AsyncClient() as http_client:
+            client = TTSClient(settings, http_client)
+            available = await client.is_available()
+
+        assert available is False