Dead code — masking is handled externally via ComfyUI. Removes
SetupWorker, MaskWorker, SettingsDialog, build_mask_output_dir,
the mask UI row, Settings button, and associated test cases.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Use SAM2VideoPredictor.from_pretrained() instead of the checkpoint-based
build_sam2_video_predictor() which doesn't accept HuggingFace model IDs.
Threshold out_mask_logits at 0.0 and squeeze shape before converting to
binary PNG.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>