feat: extract prismaudio_core model modules (DiT, conditioners, VAE, diffusion)

Fetch and adapt inference-critical model modules from upstream PrismAudio repo:
- dit.py: DiffusionTransformer with debug prints removed
- diffusion.py: ConditionedDiffusionModelWrapper, DiTWrapper, MMDiTWrapper
- conditioners.py: Cond_MLP, Sync_MLP, MultiConditioner with stubbed training imports
- autoencoders.py: AudioAutoencoder, OobleckEncoder/Decoder
- transformer.py: ContinuousTransformer, Attention with flash_attn fallback to SDPA
- blocks.py, utils.py, bottleneck.py, pretransforms.py, local_attention.py, pqmf.py
- adp.py: UNetCFG1d, UNet1d, NumberEmbedder
- mmmodules/model/low_level.py: MLP, ChannelLastConv1d, ConvMLP

All internal imports rewritten from PrismAudio.* to prismaudio_core.*,
training-only imports stubbed, flash_attn made optional with HAS_FLASH_ATTN flag.

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

prismaudio_core/models/__init__.py

@@ -0,0 +1,9 @@
+"""
+PrismAudio model modules for inference.
+
+Re-exports create_model_from_config from the factory module.
+"""
+
+from prismaudio_core.factory import create_model_from_config
+
+__all__ = ["create_model_from_config"]