feat: add language selector for voice_design + Chinese instruct support

- Generate: language dropdown (auto/English/Chinese), passed only in
  voice_design and auto_voice modes where it selects the instruct vocab
- VoiceDesign: Chinese mode with dialect/age/pitch/gender dropdowns
  using the model's validated Chinese instruct vocabulary (全角逗号)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

nodes/generator.py

@@ -62,6 +62,18 @@ class OmniVoiceGenerate:
                     "default": "",
                     "tooltip": "Transcription of ref_audio. Connect a Whisper (or other STT) node for best results.",
                 }),
+                "language": (
+                    ["auto", "English", "Chinese"],
+                    {
+                        "default": "auto",
+                        "tooltip": (
+                            "Used in voice_design mode to select the instruct vocabulary.\n"
+                            "'English' uses English instruct items (male, female, british accent …)\n"
+                            "'Chinese' uses Chinese dialect items (男, 女, 四川话, 东北话 …)\n"
+                            "Has no effect in voice_cloning mode (language is inferred from text)."
+                        ),
+                    },
+                ),
                 "instruct": ("STRING", {
                     "default": "",
                     "tooltip": (
@@ -113,11 +125,13 @@ class OmniVoiceGenerate:
     FUNCTION = "generate"
     CATEGORY = "OmniVoice"
 
-    def generate(self, model, text, mode, ref_audio=None, ref_text="",
+    def generate(self, model, text, mode, ref_audio=None, ref_text="", language="auto",
                  instruct="", guidance_scale=2.0, speed=1.0, num_step=32, seed=0):
         if seed != 0:
             torch.manual_seed(seed)
         kwargs = {"text": text, "speed": speed, "num_step": num_step, "guidance_scale": guidance_scale}
+        if mode != "voice_cloning" and language and language != "auto":
+            kwargs["language"] = language
 
         if mode == "voice_cloning" and ref_audio is None:
             raise ValueError("voice_cloning mode requires ref_audio to be connected")