feat(nix): remove devenv, build backend with nix

nix/backend.nix

@@ -0,0 +1,24 @@
+target: let
+  cargoToml = fromTOML (builtins.readFile ../backend/Cargo.toml);
+  inherit (cargoToml.package) name version;
+  pkgs = target.crossPkgs;
+  buildArgs = {
+    pname = name;
+    inherit version;
+    src = pkgs.lib.cleanSource ../.;
+    cargoLock.lockFile = ../Cargo.lock;
+    useNextest = true;
+    meta = {
+      inherit (cargoToml.package) description homepage;
+    };
+    postBuild = "${pkgs.upx}/bin/upx target/*/release/*${name}";
+  };
+  rustVersion = pkgs.rust-bin.stable.latest.default.override {
+    targets = [target.triple];
+  };
+  rustPlatform = target.crossPkgs.makeRustPlatform {
+    cargo = rustVersion;
+    rustc = rustVersion;
+  };
+in
+  rustPlatform.buildRustPackage buildArgs

nix/package.nix

@@ -1,21 +0,0 @@
-{
-  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

@@ -1,11 +0,0 @@
-{
-  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

@@ -1,58 +1,32 @@
 {
-  inputs,
   pkgs,
-  self,
   rustVersion,
-  system,
-  ...
 }:
-inputs.devenv.lib.mkShell {
-  inherit inputs pkgs;
-  modules = [
-    {
-      packages = with pkgs; [
-        # Backend
-        (rustVersion.override {
-          extensions = [
-            "clippy"
-            "rust-src"
-            "rust-analyzer"
-            "rustfmt"
-          ];
-        })
-        bacon
-        cargo-deny
-        cargo-edit
-        cargo-shuttle
-        cargo-tarpaulin
-        just
-        marksman # Markdown LSP server
-        sqlx-cli
-        tombi # TOML LSP server
-
-        # Frontend
-        nodejs_24
-        rustywind # tailwind
-        nodePackages.prettier
-        nodePackages.eslint
-        nodePackages.pnpm
+pkgs.mkShell {
+  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
+    sqlx-cli
+    tombi # TOML LSP server
 
-      processes.backend-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)"
-      '';
-    }
+    # Frontend
+    nodejs_24
+    rustywind # tailwind
+    prettier
+    eslint
+    pnpm
   ];
 }