straylight: llama.cpp 0.4.1 preset: no-mmap -> load-mode = none

0.4.1 dropped the no-mmap option (router refused to start: "option 'no-mmap'
not recognized in preset '*'"); --load-mode none is the equivalent. All other
preset keys checked against 0.4.1's option list.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

hw/straylight/default.nix

@@ -19,7 +19,8 @@ let
     cache-type-k = q8_0
     cache-type-v = q8_0
     n-gpu-layers = 999
-    no-mmap = true
+    ; llama.cpp 0.4.1 folded --no-mmap into --load-mode (none = read into memory, no mmap)
+    load-mode = none
     ; llama.cpp splits ctx-size across parallel slots: 262144 / 2 = 131072 per slot.
     ctx-size = 262144
     parallel = 2