Large contexts make the KV cache huge (a 256k q4_0 cache is several GB), which
won't fit in VRAM alongside the weights. llama.cpp can't page KV to disk, but it
can keep it in system RAM via --no-kv-offload. Expose that as a per-model
kv_offload flag (default unchanged = KV in VRAM): set kv_offload=false to pass
offload_kqv=False to llama.cpp, freeing VRAM for big contexts at the cost of
slower decode (KV ops cross PCIe). Also allow the key in the admin model-config
endpoint so it's persistable from the UI.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>