fix: replace custom Pivoine node with direct DiffRhythm patch

- Remove custom PivoineDiffRhythmRun wrapper node
- Add git patch file for ComfyUI_DiffRhythm __init__.py
- Patch adds LlamaConfig fix at import time
- Add arty script 'fix/diffrhythm-patch' to apply patch
- Revert all workflows to use original DiffRhythmRun
- Remove startup_patch.py and revert start.sh

This approach is cleaner and more maintainable than wrapping the node.
The patch directly fixes the tensor dimension mismatch (32 vs 64) in
DiffRhythm's rotary position embeddings by ensuring num_attention_heads
and num_key_value_heads are properly set based on hidden_size.

References:
- https://github.com/billwuhao/ComfyUI_DiffRhythm/issues/44
- https://github.com/billwuhao/ComfyUI_DiffRhythm/issues/48

comfyui/workflows/text-to-music/diffrhythm-full-length-t2m-v1.json

@@ -4,7 +4,7 @@
   "nodes": [
     {
       "id": 1,
-      "type": "PivoineDiffRhythmRun",
+      "type": "DiffRhythmRun",
       "pos": [100, 100],
       "size": [400, 400],
       "flags": {},

comfyui/workflows/text-to-music/diffrhythm-random-generation-v1.json

@@ -4,7 +4,7 @@
   "nodes": [
     {
       "id": 1,
-      "type": "PivoineDiffRhythmRun",
+      "type": "DiffRhythmRun",
       "pos": [100, 100],
       "size": [400, 400],
       "flags": {},

comfyui/workflows/text-to-music/diffrhythm-reference-based-v1.json

@@ -27,7 +27,7 @@
     },
     {
       "id": 2,
-      "type": "PivoineDiffRhythmRun",
+      "type": "DiffRhythmRun",
       "pos": [500, 100],
       "size": [400, 450],
       "flags": {},

comfyui/workflows/text-to-music/diffrhythm-simple-t2m-v1.json

@@ -4,7 +4,7 @@
   "nodes": [
     {
       "id": 1,
-      "type": "PivoineDiffRhythmRun",
+      "type": "DiffRhythmRun",
       "pos": [100, 100],
       "size": [400, 400],
       "flags": {},