frank-default-small: use split-mode none on single-GPU dankserver

--split-mode graph requires >= 2 devices in ik_llama.cpp and errors hard
at model load on a single RTX 3090 ("It is not possible to use split mode
'graph' with less than 2 devices"), looping the service. Set SPLIT_MODE
=none (the default), which works with the --override-tensor CPU expert
offload. KB updated with the two-device requirement so we do not assume
graph degrades gracefully on one GPU.

scripts/serve-frank-small.sh

@@ -10,10 +10,8 @@
 # KV cache: q8_KV with Hadamard transforms on K and V (requires a build with
 # GGML_CUDA_FA_ALL_QUANTS=ON + GGML_IQK_FA_ALL_QUANTS=ON; see the env file).
 #
-# Split mode graph + --override-tensor CPU expert offload. Per ik_llama
-# README, `--split-mode graph` + partial GPU offload can occasionally produce
-# incoherent output; the documented fallback is `-cuda graphs=0`. Smoke-test
-# after each model load.
+# Split mode is none: Dankserver has a single RTX 3090 and ik_llama rejects
+# split-mode graph with fewer than 2 devices (hard load error).
 #
 # Expert offload: the expert (FFN exps) tensors selected by the layer-bounded
 # --override-tensor pattern are pinned to CPU. Selected full-attention and