feat: add Voice Design node + language and guidance_scale to Generate

OmniVoiceVoiceDesign: structured dropdowns for gender/age/pitch/accent
that compose into an instruct string — wire to Generate's instruct input.

OmniVoiceGenerate: new optional language dropdown (auto + 11 languages)
and guidance_scale (CFG, default 2.0) parameters.

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

nodes/voice_design.py

@@ -0,0 +1,32 @@
+class OmniVoiceVoiceDesign:
+    """Compose a voice design instruct string from structured dropdowns."""
+
+    GENDERS  = ["none", "male", "female"]
+    AGES     = ["none", "child", "teenager", "young adult", "middle-aged", "elderly"]
+    PITCHES  = ["none", "very low pitch", "low pitch", "moderate pitch", "high pitch", "very high pitch", "whisper"]
+    ACCENTS  = [
+        "none",
+        "american accent", "british accent", "australian accent", "canadian accent",
+        "indian accent", "chinese accent", "japanese accent", "korean accent",
+        "portuguese accent", "russian accent",
+    ]
+
+    @classmethod
+    def INPUT_TYPES(cls):
+        return {
+            "required": {
+                "gender": (cls.GENDERS, {"default": "female"}),
+                "age":    (cls.AGES,    {"default": "none"}),
+                "pitch":  (cls.PITCHES, {"default": "none"}),
+                "accent": (cls.ACCENTS, {"default": "none"}),
+            },
+        }
+
+    RETURN_TYPES  = ("STRING",)
+    RETURN_NAMES  = ("instruct",)
+    FUNCTION      = "compose"
+    CATEGORY      = "OmniVoice"
+
+    def compose(self, gender, age, pitch, accent):
+        parts = [v for v in [gender, age, pitch, accent] if v != "none"]
+        return (", ".join(parts),)