feat: rust project initialization

nix/package.nix

@@ -0,0 +1,21 @@
+{
+  pkgs,
+  rustPlatform,
+  ...
+}: let
+  cargoToml = builtins.fromTOML (builtins.readFile ../Cargo.toml);
+  name = cargoToml.package.name;
+  version = cargoToml.package.version;
+  rustBuild = rustPlatform.buildRustPackage {
+    pname = name;
+    inherit version;
+    src = ../.;
+    cargoLock.lockFile = ../Cargo.lock;
+  };
+  settingsDir = pkgs.runCommand "settings" {} ''
+    mkdir -p $out/settings
+    cp ${../settings}/*.yaml $out/settings/
+  '';
+in {
+  jj-mcp = rustBuild;
+}

nix/rust-version.nix

@@ -0,0 +1,11 @@
+{
+  rust-overlay,
+  inputs,
+  system,
+  ...
+}: let
+  overlays = [(import rust-overlay)];
+in rec {
+  pkgs = import inputs.nixpkgs {inherit system overlays;};
+  version = pkgs.rust-bin.stable.latest.default;
+}

nix/shell.nix

@@ -0,0 +1,49 @@
+{
+  inputs,
+  pkgs,
+  self,
+  rustVersion,
+  system,
+  ...
+}:
+inputs.devenv.lib.mkShell {
+  inherit inputs pkgs;
+  modules = [
+    {
+      packages = with pkgs; [
+        (rustVersion.override {
+          extensions = [
+            "clippy"
+            "rust-src"
+            "rust-analyzer"
+            "rustfmt"
+          ];
+        })
+        bacon
+        cargo-deny
+        cargo-edit
+        cargo-shuttle
+        cargo-tarpaulin
+        just
+        marksman # Markdown LSP server
+        tombi # TOML LSP server
+      ];
+
+      processes.run.exec = "bacon run";
+
+      enterShell = ''
+        echo "🦀 Rust MCP development environment loaded!"
+        echo "📦 Rust version: $(rustc --version)"
+        echo "📦 Cargo version: $(cargo --version)"
+        echo ""
+        echo "Available tools:"
+        echo "  - rust-analyzer (LSP)"
+        echo "  - clippy (linter)"
+        echo "  - rustfmt (formatter)"
+        echo "  - bacon (continuous testing/linting)"
+        echo "  - cargo-deny (dependency checker)"
+        echo "  - cargo-tarpaulin (code coverage)"
+      '';
+    }
+  ];
+}