feat(merge): add dedicated CWB mergers

docs/consensus_mergers.md

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+# Consensus-Weighted Blending Mergers
+
+The dedicated CWB nodes merge two or three safetensors files using
+Consensus-Weighted Blending. They calculate an element-wise mean or median
+consensus, compare each aligned source vector to that consensus, and normalize
+similarity-derived weights before producing the output vector.
+
+## Node families
+
+Two-input and three-input variants are provided for checkpoints, standalone
+diffusion models, text encoders, LoRAs, and embeddings.
+
+Checkpoint, diffusion-model, text-encoder, and LoRA outputs are anchored to
+Model A. Model A supplies the output key set, metadata, and naming. Keys found
+only in later inputs are ignored. Embedding mergers instead use the union of
+all keys and use the longest compatible first dimension as the alignment
+reference.
+
+## Presets and custom controls
+
+`baseline` is the default. The standard clarity, smooth, varied, and diversity
+presets are joined by `power_blend` and the DSC presets demonstrated by the CWB
+conditioning implementation. Select `custom` to make every manual CWB control
+authoritative.
+
+Similarity alignment greedily matches source rows to the reference by cosine
+similarity. Index alignment keeps absolute row positions. Position weight can
+bias similarity matches toward nearby normalized positions. Preserve Common
+Prefix copies the longest numerically identical leading row span directly from
+the first input.
+
+Inputs have equal prior weight. The similarity calculation supplies the
+effective contribution for each aligned vector. If every candidate is rejected
+or receives zero weight, CWB falls back to equal weighting.
+
+## Missing tensors and filtering
+
+- `skip` preserves Model A when an anchored input is missing or incompatible.
+  In embedding-union mode it omits that source for the affected key.
+- `zeros` supplies a compatible zero tensor for the missing source.
+- `error` stops the merge.
+- Exclude patterns preserve the anchored source tensor.
+- Discard patterns remove the matching output tensor or logical LoRA layer.
+
+Patterns use regular expressions by default. Enable Glob Patterns to use glob
+syntax instead.
+
+## LoRA behavior
+
+LoRA inputs use the same parser as the resize and multi-merge nodes. This
+includes the repository's plain `.lora_A.weight` / `.lora_B.weight` extraction
+output, already-supported alternative A/B or down/up suffixes, and direct
+`.diff` / `.diff_b` layers.
+
+Model A's exact keys and suffix convention are retained. Secondary formats are
+matched by normalized logical layer name. Differing ranks are zero-padded like
+the DARE/TIES mergers: A/down tensors on dimension 0 and B/up tensors on
+dimension 1. An existing Model A alpha key is updated to the resulting maximum
+rank; no alpha key is invented when Model A has none. Incomplete pairs,
+auxiliary tensors, and unrecognized Model A tensors are copied unchanged.
+
+`include_1d_diffs` is disabled by default. Disabled 1D direct layers preserve
+Model A. Enabled 1D direct layers participate as complete tensors and are
+always saved in FP32.
+
+## Precision and quantized inputs
+
+CWB computes in FP32. Unless Override Dtype is enabled, any participating FP32
+source keeps the generated logical layer in FP32. Guarded low-bit tensors and
+enabled 1D direct diffs are never downcast by the override.
+
+ComfyUI/comfy-kitchen quantized inputs are rejected before an output writer is
+opened. Files with three or more bare INT8, UINT8, FP8, or FP4 tensors are also
+rejected. One or two isolated low-bit tensors produce one warning per input and
+are preserved without CWB arithmetic; an affected LoRA causes its complete
+logical layer to be preserved.