[Hendrik-code]

What

One config, transform_params_paper-palette-clean.json (hash ba46ce7b). It is the Palette alone arm plus three RandomPaletteGPU keys. Palette alone is transform_params_paper-synthseg.json with RandomSynthSegGPU replaced by RandomPaletteGPU at p: 1.0, hash 4b92045c, the same config #142 ships as transform_params_paper-palette.json.

key	value	removes
skip_sub_parc_prob	1.0	the Voronoi sub-parcellation, which cuts straight polygon edges through anatomy: edges no imaging modality produces
label_remap_prob	0.0	the per-label affine remap, which steps the intensity exactly on the ground-truth boundary
blur_sigmas	[0.5, 0.8]	unblurred speckle: the k-means bucketing is hard, so voxels next to a cluster threshold flip between two remaps

Every other key is Palette alone's, so the two differ only in these three. No code change: all three are existing RandomPaletteGPU parameters. Based on main rather than #142, so it does not wait on that PR; the .gitignore entry is its own.

Why

Seen in renders of the PALETTE arm on four SpineGAN datasets:

• polygonal regions crossing vertebrae;
• salt-and-pepper, worst on CT;
• label-shaped steps.

In 9 of 40 measured feature-only samples, intensity no longer separated the labels at all. The config asks whether PALETTE's measured gain on Dataset804 survives without those artifacts.

Tests

unit_tests/test_palette_clean_config.py:

• the config sets the three knobs and has no SynthSeg;
• it builds and runs;
• with Voronoi and label remap off (blur off for the check), voxels of equal input intensity map to equal outputs across both labels, over five seeds;
• the defaults break that, so the check can fail.

Full suite: 477 passed, 13 skipped. Pre-commit passes.

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