fix(tts): update MiniMax API endpoint to v1/text_to_speech

MiniMax deprecated the old v1/t2a_v2 endpoint (api.minimax.io) and
moved to v1/text_to_speech (api.minimax.chat). The new API:

- Uses a flat payload: {model, text, voice_id} instead of nested
  voice_setting / audio_setting objects
- Returns raw audio bytes (Content-Type: audio/mpeg) instead of
  JSON with hex-encoded audio
- Uses model 'speech-01' instead of 'speech-2.8-hd'
- Updated default voice_id to 'female-shaonv' for Chinese TTS

The implementation detects Content-Type to handle both old and new
API responses, maintaining backward compatibility for any users who
manually configured the legacy base_url.

tools/tts_tool.py

@@ -136,9 +136,9 @@ DEFAULT_KITTENTTS_VOICE = "Jasper"
 DEFAULT_PIPER_VOICE = "en_US-lessac-medium"  # balanced size/quality
 DEFAULT_OPENAI_VOICE = "alloy"
 DEFAULT_OPENAI_BASE_URL = "https://api.openai.com/v1"
-DEFAULT_MINIMAX_MODEL = "speech-2.8-hd"
-DEFAULT_MINIMAX_VOICE_ID = "English_Graceful_Lady"
-DEFAULT_MINIMAX_BASE_URL = "https://api.minimax.io/v1/t2a_v2"
+DEFAULT_MINIMAX_MODEL = "speech-01"
+DEFAULT_MINIMAX_VOICE_ID = "female-shaonv"
+DEFAULT_MINIMAX_BASE_URL = "https://api.minimax.chat/v1/text_to_speech"
 DEFAULT_MISTRAL_TTS_MODEL = "voxtral-mini-tts-2603"
 DEFAULT_MISTRAL_TTS_VOICE_ID = "c69964a6-ab8b-4f8a-9465-ec0925096ec8"  # Paul - Neutral
 DEFAULT_XAI_VOICE_ID = "eve"
@@ -925,10 +925,11 @@ def _generate_xai_tts(text: str, output_path: str, tts_config: Dict[str, Any]) -
 # ===========================================================================
 def _generate_minimax_tts(text: str, output_path: str, tts_config: Dict[str, Any]) -> str:
     """
-    Generate audio using MiniMax TTS API.
+    Generate audio using MiniMax TTS API (v1/text_to_speech).
 
-    MiniMax returns hex-encoded audio data. Supports streaming (SSE) and
-    non-streaming modes. This implementation uses non-streaming for simplicity.
+    The current API (api.minimax.chat/v1/text_to_speech) uses a simple payload
+    and returns raw audio bytes directly (Content-Type: audio/mpeg), unlike
+    the deprecated v1/t2a_v2 endpoint which returned JSON with hex-encoded audio.
 
     Args:
         text: Text to convert (max 10,000 characters).
@@ -947,35 +948,12 @@ def _generate_minimax_tts(text: str, output_path: str, tts_config: Dict[str, Any
     mm_config = tts_config.get("minimax", {})
     model = mm_config.get("model", DEFAULT_MINIMAX_MODEL)
     voice_id = mm_config.get("voice_id", DEFAULT_MINIMAX_VOICE_ID)
-    speed = mm_config.get("speed", tts_config.get("speed", 1))
-    vol = mm_config.get("vol", 1)
-    pitch = mm_config.get("pitch", 0)
     base_url = mm_config.get("base_url", DEFAULT_MINIMAX_BASE_URL)
 
-    # Determine audio format from output extension
-    if output_path.endswith(".wav"):
-        audio_format = "wav"
-    elif output_path.endswith(".flac"):
-        audio_format = "flac"
-    else:
-        audio_format = "mp3"
-
     payload = {
         "model": model,
         "text": text,
-        "stream": False,
-        "voice_setting": {
-            "voice_id": voice_id,
-            "speed": speed,
-            "vol": vol,
-            "pitch": pitch,
-        },
-        "audio_setting": {
-            "sample_rate": 32000,
-            "bitrate": 128000,
-            "format": audio_format,
-            "channel": 1,
-        },
+        "voice_id": voice_id,
     }
 
     headers = {
@@ -984,9 +962,25 @@ def _generate_minimax_tts(text: str, output_path: str, tts_config: Dict[str, Any
     }
 
     response = requests.post(base_url, json=payload, headers=headers, timeout=60)
-    response.raise_for_status()
 
-    result = response.json()
+    content_type = response.headers.get("Content-Type", "")
+
+    if "audio/" in content_type:
+        # New API: returns raw audio directly
+        with open(output_path, "wb") as f:
+            f.write(response.content)
+        return output_path
+
+    # Legacy / fallback: try parsing as JSON with hex-encoded audio
+    try:
+        result = response.json()
+    except Exception:
+        response.raise_for_status()
+        raise RuntimeError(
+            f"MiniMax TTS returned unexpected Content-Type '{content_type}' "
+            f"({len(response.content)} bytes)"
+        )
+
     base_resp = result.get("base_resp", {})
     status_code = base_resp.get("status_code", -1)
 
@@ -998,7 +992,7 @@ def _generate_minimax_tts(text: str, output_path: str, tts_config: Dict[str, Any
     if not hex_audio:
         raise RuntimeError("MiniMax TTS returned empty audio data")
 
-    # MiniMax returns hex-encoded audio (not base64)
+    # Legacy: hex-encoded audio
     audio_bytes = bytes.fromhex(hex_audio)
 
     with open(output_path, "wb") as f: