feat(packages): add llama-cpp b9645 for Strix Halo (ROCm + Vulkan)

Pin upstream llama.cpp b9645 and build it against the nixpkgs-latest
input (the flake's pinned nixpkgs only carries the pre-tools/ui b8983).
ROCm deps come from rocmPackages.gfx1151, so clr/rocBLAS/hipBLAS are
built for gfx1151 only; clr's own build is arch-independent, so its
store path stays substitutable. Vulkan on, CPU variants with znver5 /
AVX-512, web UI and npm toolchain dropped.

Ported from nixos-config's llm-engine.nix with two fixes: npmConfigHook
hard-fails when npmDeps is null, so nodejs and the hook are stripped
from nativeBuildInputs, and CMAKE_HIP_FLAGS is appended to
cmakeFlagsArray because the cmake hook word-splits plain cmakeFlags.

Verified on the Radeon 8060S (gfx1151): llama-bench loads both ROCm and
Vulkan backends and completes pp16/tg8 runs.

README.md

@@ -27,6 +27,7 @@ A custom Nix overlay and flake providing additional packages not found in upstre
 | `nftablesbuilder` | Web interface to manage nftables rules with drag-and-drop rule creation | Networking |
 | `skillsmcp` | MCP server that exposes Agent Skills to AI agents via the Model Context Protocol | MCP Servers |
 | `kubernetes-mcp-server` | Model Context Protocol (MCP) server for Kubernetes and OpenShift | MCP Servers |
+| `llama-cpp` | llama.cpp pinned to build b9645, built for Strix Halo (gfx1151) with ROCm + Vulkan backends | AI Inference |
 | `loop` | Corporate messenger for your team | Communication |
 | `radar` | Modern Kubernetes visibility — topology, event timeline, service traffic, resource browsing, Helm management, and GitOps support | Kubernetes |
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