fix: decode opus manually and use json audio transcription

tests/test_openrouter_client.py

@@ -0,0 +1,25 @@
+import base64
+import os
+import sys
+from pathlib import Path
+
+sys.path.insert(0, os.path.dirname(os.path.dirname(__file__)))
+
+from openrouter_client import _audio_format, _build_transcription_payload
+
+
+def test_audio_format_defaults_to_wav_when_missing_suffix(tmp_path: Path):
+    path = tmp_path / "recording"
+    path.write_bytes(b"abc")
+    assert _audio_format(str(path)) == "wav"
+
+
+def test_build_transcription_payload_uses_base64_json_shape(tmp_path: Path):
+    path = tmp_path / "meeting.wav"
+    path.write_bytes(b"RIFFdemo")
+
+    payload = _build_transcription_payload(str(path))
+
+    assert payload["model"] == "openai/whisper-large-v3"
+    assert payload["input_audio"]["format"] == "wav"
+    assert payload["input_audio"]["data"] == base64.b64encode(b"RIFFdemo").decode("ascii")