feat(shardr): Add shardr package to the overlay

Decentralized LLM repository (Go): content-addressed model store with
BitTorrent-based sync and OpenAI-compatible serving via llama-server.
Upstream has no tagged source releases, so the package is pinned to
main HEAD (fab7fa8) with a nix-update script targeting the branch.
Builds both shardr and shardhive binaries.

README.md

@@ -27,6 +27,7 @@ A custom Nix overlay and flake providing additional packages not found in upstre
 | `mcp-gateway` | Universal Model Context Protocol gateway that sits between AI client and MCP tools/servers | MCP Servers |
 | `nftables-analyzer` | Analyze nftables firewall rules and evaluate traffic queries | Networking |
 | `nftablesbuilder` | Web interface to manage nftables rules with drag-and-drop rule creation | Networking |
+| `shardr` | Decentralized LLM repository: content-addressed model store, BitTorrent-based sync, OpenAI-compatible serving via llama-server | AI Inference |
 | `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 |