chore: remove all PrismAudio code from main branch

- Delete prismaudio_core/, data_utils/, scripts/, docs/plans/
- Delete PrismAudio nodes (feature_extractor, feature_loader, model_loader, sampler, text_only)
- Delete PrismAudio workflows (video_to_audio, text_to_audio)
- Clean nodes/utils.py: rename PRISMAUDIO_CATEGORY → SELVA_CATEGORY, remove unused helpers
- Strip PrismAudio-only deps from requirements.txt

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

nodes/selva_model_loader.py

@@ -3,7 +3,7 @@ from pathlib import Path
 import torch
 import folder_paths
 
-from .utils import PRISMAUDIO_CATEGORY, get_offload_device, determine_offload_strategy
+from .utils import SELVA_CATEGORY, get_offload_device, determine_offload_strategy
 
 # Variant → (generator filename, mode, has_bigvgan)
 _VARIANTS = {
@@ -96,7 +96,7 @@ class SelvaModelLoader:
     RETURN_TYPES = ("SELVA_MODEL",)
     RETURN_NAMES = ("model",)
     FUNCTION = "load_model"
-    CATEGORY = PRISMAUDIO_CATEGORY
+    CATEGORY = SELVA_CATEGORY
 
     def load_model(self, variant, precision, offload_strategy):
         from selva_core.model.networks_generator import get_my_mmaudio