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/frank-default-small.env

@@ -76,9 +76,11 @@ CACHE_TYPE_V=q8_KV
 K_CACHE_HADAMARD=1
 V_CACHE_HADAMARD=1
 
-# Split mode: graph (multi-GPU graph split; on a single 3090 this is a no-op
-# for correctness but kept per operator preference).
-SPLIT_MODE=graph
+# Split mode: none. Dankserver has a single RTX 3090 and ik_llama requires
+# >= 2 devices for split-mode graph ('It is not possible to use split mode
+# graph with less than 2 devices' is a hard load error). none is correct
+# here and still works with OVERRIDE_EXPERT CPU expert offload.
+SPLIT_MODE=none
 
 VERBOSITY=4
 # Store context checkpoints in RAM to hold peak GPU memory down.