feat: add Nix flake for native Nix/NixOS installation

.gitignore

@@ -50,3 +50,6 @@ test-languages/
 
 nul
 release/
+
+# Nix
+result

flake.nix

@@ -0,0 +1,85 @@
+{
+  description = "CodeGraph – semantic code intelligence for AI agents";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+
+        nodejs = pkgs.nodejs_24;
+
+        codegraph = pkgs.buildNpmPackage {
+          pname = "codegraph";
+          version =
+            (builtins.fromJSON (builtins.readFile ./package.json)).version;
+
+          src = ./.;
+
+          npmDeps = pkgs.fetchNpmDeps {
+            src = ./.;
+            hash = "sha256-GJfqzykgrgD/KCtf8LupRw31S2cCmwGCF/0PMpzaCrk=";
+          };
+
+          inherit nodejs;
+
+          npmBuildScript = "build";
+
+          # The build copies .wasm + schema.sql into dist/ via the
+          # `copy-assets` npm script (called from `build`).  Nothing
+          # extra to do here.
+
+          installPhase = ''
+            runHook preInstall
+
+            # Application code
+            mkdir -p $out/lib/codegraph
+            cp -r dist $out/lib/codegraph/dist
+            cp package.json $out/lib/codegraph/
+
+            # Production node_modules (already populated by buildNpmPackage)
+            cp -r node_modules $out/lib/codegraph/node_modules
+
+            # Launcher wrapper: injects --liftoff-only so tree-sitter's
+            # large WASM grammars stay on V8's Liftoff baseline compiler
+            # and never hit the turboshaft Zone OOM (issues #293/#298).
+            mkdir -p $out/bin
+            cat > $out/bin/codegraph <<'EOF'
+#!/bin/sh
+exec @node@ --liftoff-only @out@/lib/codegraph/dist/bin/codegraph.js "$@"
+EOF
+            substituteInPlace $out/bin/codegraph \
+              --replace-fail '@node@' '${nodejs}/bin/node' \
+              --replace-fail '@out@' "$out"
+            chmod +x $out/bin/codegraph
+
+            runHook postInstall
+          '';
+
+          # No native addons to build — pure JS + WASM.
+          dontNpmBuild = false;
+
+          meta = with pkgs.lib; {
+            description =
+              "Semantic code intelligence for AI agents — local-first knowledge graph over tree-sitter";
+            homepage = "https://github.com/colbymchenry/codegraph";
+            license = licenses.mit;
+            mainProgram = "codegraph";
+            platforms = platforms.unix;
+          };
+        };
+      in {
+        packages = {
+          default = codegraph;
+          inherit codegraph;
+        };
+
+        devShells.default = pkgs.mkShell {
+          buildInputs = [ nodejs ];
+        };
+      });
+}