fix: SelvaSampler — negative_prompt above settings

Move negative_prompt to required inputs, right after prompt, so it appears
above duration/steps/cfg/seed in the ComfyUI node layout.

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

nodes/selva_sampler.py

@@ -15,6 +15,10 @@ class SelvaSampler:
                     "default": "", "multiline": True,
                     "tooltip": "CLIP text for audio generation. Leave empty to reuse the prompt from SelvaFeatureExtractor.",
                 }),
+                "negative_prompt": ("STRING", {
+                    "default": "", "multiline": True,
+                    "tooltip": "Sounds to steer away from, e.g. 'wind noise, background music'.",
+                }),
                 "duration": ("FLOAT", {
                     "default": 0.0, "min": 0.0, "max": 30.0, "step": 0.1,
                     "tooltip": "Audio duration in seconds. 0 = use duration from features.",
@@ -25,12 +29,7 @@ class SelvaSampler:
                                            "tooltip": "CFG scale (SelVA default is 4.5)."}),
                 "seed":     ("INT",   {"default": 0,   "min": 0,   "max": 0xFFFFFFFF}),
             },
-            "optional": {
-                "negative_prompt": ("STRING", {
-                    "default": "", "multiline": True,
-                    "tooltip": "Sounds to steer away from, e.g. 'wind noise, background music'.",
-                }),
-            },
+            "optional": {},
         }
 
     RETURN_TYPES = ("AUDIO",)
@@ -38,7 +37,7 @@ class SelvaSampler:
     FUNCTION = "generate"
     CATEGORY = PRISMAUDIO_CATEGORY
 
-    def generate(self, model, features, prompt, duration, steps, cfg_strength, seed, negative_prompt=None):
+    def generate(self, model, features, prompt, negative_prompt, duration, steps, cfg_strength, seed):
         from selva_core.model.flow_matching import FlowMatching
         from selva_core.model.sequence_config import SequenceConfig
 
@@ -96,7 +95,7 @@ class SelvaSampler:
 
             # Encode negative prompt (or use empty conditions)
             neg_text_clip = feature_utils.encode_text_clip([negative_prompt]) \
-                if negative_prompt and negative_prompt.strip() else None
+                if negative_prompt.strip() else None
 
             conditions = net_generator.preprocess_conditions(clip_f, sync_f, text_clip)
             empty_conditions = net_generator.get_empty_conditions(