feat(tts): add Xiaomi MiMo text-to-speech support

Adds mimo-v2.5-tts as a Media Provider TTS through the existing
OpenAI-compatible chat-completions endpoint. Voice is selected via the
top-level audio.voice field, and an optional style/language hint is
threaded through tts.js -> ttsCore.js -> the new adapter.

open-sse/config/ttsModels.js

@@ -33,6 +33,21 @@ const GEMINI_VOICES = [
   "Vindemiatrix", "Sadachbia", "Sadaltager", "Sulafat",
 ].map((id) => ({ id, name: id, type: "tts" }));
 
+// Xiaomi MiMo preset voices (from https://mimo.mi.com/docs/zh-CN/quick-start/usage-guide/audio/speech-synthesis-v2.5).
+// Voice id is passed via `audio.voice`; `mimo_default` = default (冰糖 on CN cluster, Mia elsewhere).
+// Voices are language-independent — the spoken language is a separate hint, not bound to the voice.
+const MIMO_VOICES = [
+  { id: "mimo_default", name: "mimo_default" },
+  { id: "冰糖",           name: "冰糖" },
+  { id: "茉莉",           name: "茉莉" },
+  { id: "苏打",           name: "苏打" },
+  { id: "白桦",           name: "白桦" },
+  { id: "Mia",           name: "Mia" },
+  { id: "Chloe",         name: "Chloe" },
+  { id: "Milo",          name: "Milo" },
+  { id: "Dean",          name: "Dean" },
+].map((v) => ({ type: "tts", ...v }));
+
 // ── TTS Config (config-driven, single source of truth) ─────────────────────
 export const TTS_MODELS_CONFIG = {
   openai: {
@@ -107,6 +122,14 @@ export const TTS_MODELS_CONFIG = {
     },
     allVoices: GEMINI_VOICES,
   },
+  "xiaomi-mimo": {
+    models: [
+      { id: "mimo-v2.5-tts", name: "MiMo V2.5 TTS", type: "tts" },
+    ],
+    voices: {
+      "mimo-v2.5-tts": MIMO_VOICES,
+    },
+  },
 };
 
 // ── Helper: get voices for a specific model ────────────────────────────────