docs(llama-cpp): deployment detail goes back to the setup page

The overview page carried `docker run` invocations (including a CUDA variant, on a fleet with no
NVIDIA card left in it) and the `LLAMA_ARG_` environment rule, while `setup.md` — the page whose
own intro promises "build instructions, Docker, and systemd deployment" — carried the Compose
example and the same env form in use. Two places to look, one place to be wrong.

`setup.md` now states the env-prefix rule where the flags live (and why units prefer it: one
flag per line is auditable, a forty-flag command line is not), and the overview keeps only the
API surface and the GGUF format, pointing at the sections that absorbed the rest.

Refs #64

omp-docs/tools/llama-cpp/setup.md

@@ -111,6 +111,14 @@ cmake --build build --config Release -t llama-server
 | `-lora FNAME` | LoRA adapter (repeatable) | — |
 | `-ngl, --gpu-layers N` | Layers to offload to GPU | auto |
 
+### Environment Variables
+
+Every CLI option can be set from the environment instead: prefix the upper-snake form of the
+long flag with `LLAMA_ARG_` — `LLAMA_ARG_MODEL=/models/model.gguf LLAMA_ARG_CTX_SIZE=8192
+llama-server`. This is how the container and systemd units pass configuration (see the Compose
+example below), because a unit file with one flag per line is auditable and a shell command line
+with forty is not.
+
 ### Context & Performance
 
 | Flag | Description | Default |