* metal : support scale-bias routing norm in the TOPK_MOE fusion

The DeepSeek-V4.1 graph normalizes the routing weights with a scale+bias
(sum + 1e-20) instead of the lower clamp used by the other models. Add
norm_bias/norm_scale_bias fusion chains that accept a SCALE node with a
unit scale factor at the clamp position, pass an additive bias in the
kernel args, and apply it as max(wt_sum, clamp) + bias so both variants
share one kernel. Cover the new chains in test-backend-ops.

Assisted-by: dsh:llama.cpp/ggml-org/GLM-5.3-Flash-GGUF (Mac Studio, M5 Ultra, 256GB)

* metal : fuse sqrt(softplus) MoE routing with a selection bias

Add TOPK_MOE chains anchored at the softplus node (UNARY+SQRT+ADD+
ARGSORT+GET_ROWS plus optional norm/scale) so the DeepSeek-V4/V4.1
routing fuses on Metal. The kernel scores with sqrt(softplus) and ranks
selection-biased keys while the gathered weights and the norm stay
unbiased, matching the reference graph. Dispatch hooks at the softplus
node, cover the norm-bias combination in test-backend-ops and record the
new deepseek4/deepseek41 fusion counters.

Assisted-by: dsh:llama.cpp/ggml-org/GLM-5.3-Flash-GGUF (Mac Studio, M5 Ultra, 256GB)

* metal : fuse sigmoid MoE routing with a selection bias

The sigmoid-gated MoE archs (GLM, DeepSeek-V2/V3.2, ...) rank
sigmoid(logits) + exp_probs_b with an optional weights-norm, but only
the softmax and sqrt(softplus) routing chains were fusable.

- add 6 sigmoid-anchored TOPK_MOE chains: sigmoid + ADD + ARGSORT +
  GET_ROWS with optional SCALE and SUM_ROWS + CLAMP/SCALE + DIV norm
  tail; the selection-bias ADD is required, same as the sqrt(softplus)
  chains
- generalize the gating function constant from a sqrt(softplus) bool
  to an int (0 = softmax, 1 = sqrt(softplus), 2 = sigmoid); sigmoid
  scores are 1 / (1 + exp(-logits)), matching the CPU, Metal unary and
  CUDA kernels
- anchor the unary dispatch hook at sigmoid nodes too
- test-backend-ops: 4 sigmoid routing cases with and without a
  weights scale
- re-record tests/fusion/MTL.csv: the sigmoid archs (glm5-next,
  deepseek2/32, kimi, minimax, ...) now fuse their routing, and
  muse-spark prefill drops one MOE_REDUCE fire because the reordered
  graph allocates the routing weights inside the reduce output range,
  which the dst/input overlap check correctly declines

Assisted-by: dsh:llama.cpp/ggml-org/GLM-5.3-Flash-GGUF (Mac Studio, M5 Ultra, 256GB)

* cont : remove low-signal comments

* ocd : valign ggml_metal_fusions