chore: vendor selva_core from jnwnlee/selva@d7d40a9

Pure PyTorch SelVA source for SelvaModelLoader/FeatureExtractor/Sampler nodes.
Imports rewritten from selva.* to selva_core.*. mel_converter.py: replaced
librosa.filters.mel with pure-numpy implementation to avoid librosa→numba→NumPy
version incompatibility in some ComfyUI environments.

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

selva_core/utils/dist_utils.py

@@ -0,0 +1,17 @@
+import os
+from logging import Logger
+
+from selva_core.utils.logger import TensorboardLogger
+
+local_rank = int(os.environ['LOCAL_RANK']) if 'LOCAL_RANK' in os.environ else 0
+world_size = int(os.environ['WORLD_SIZE']) if 'WORLD_SIZE' in os.environ else 1
+
+
+def info_if_rank_zero(logger: Logger, msg: str):
+    if local_rank == 0:
+        logger.info(msg)
+
+
+def string_if_rank_zero(logger: TensorboardLogger, tag: str, msg: str):
+    if local_rank == 0:
+        logger.log_string(tag, msg)