fix: guard model cleanup in try/finally and fix DiTWrapper comments

- Wrap training loop in try/finally so _unapply_lora always runs.
  Without this, an exception mid-training would leave LoRALinear wrappers
  in the cached DiTWrapper; a subsequent training run would then apply LoRA
  on top of existing LoRA, silently doubling the effective rank.
- Fix misleading comment: diffusion.model is DiTWrapper (not DiffusionTransformer).
  DiffusionTransformer is at diffusion.model.model; _apply_lora reaches it
  recursively but the direct attribute is the wrapper.

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

nodes/lora_loader.py

@@ -95,7 +95,7 @@ class PrismAudioLoRALoader:
         # Merge LoRA weights in-place into the DiT's base linear layers.
         # ComfyUI re-executes the upstream ModelLoader on the next queue run
         # when inputs change, providing a fresh base model as needed.
-        dit = model["model"].model  # DiffusionTransformer
+        dit = model["model"].model  # DiTWrapper
 
         if strength == 0.0:
             print("[PrismAudio] LoRA strength=0.0 — skipping merge, base model unchanged.", flush=True)