Add custom nodes, Civitai loras (LFS), and vast.ai setup script

Includes 30 custom nodes committed directly, 7 Civitai-exclusive
loras stored via Git LFS, and a setup script that installs all
dependencies and downloads HuggingFace-hosted models on vast.ai.

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

custom_nodes/ComfyUI-KJNodes/utility/numerical.py

@@ -0,0 +1,25 @@
+from functools import reduce
+from itertools import cycle
+from math import factorial
+
+import numpy as np
+import scipy.sparse as sp
+
+
+def difference(derivative, accuracy=1):
+    # Central differences implemented based on the article here:
+    # http://web.media.mit.edu/~crtaylor/calculator.html
+    derivative += 1
+    radius = accuracy + derivative // 2 - 1
+    points = range(-radius, radius + 1)
+    coefficients = np.linalg.inv(np.vander(points))
+    return coefficients[-derivative] * factorial(derivative - 1), points
+
+
+def operator(shape, *differences):
+    # Credit to Philip Zucker for figuring out
+    # that kronsum's argument order is reversed.
+    # Without that bit of wisdom I'd have lost it.
+    differences = zip(shape, cycle(differences))
+    factors = (sp.diags(*diff, shape=(dim,) * 2) for dim, diff in differences)
+    return reduce(lambda a, f: sp.kronsum(f, a, format='csc'), factors)