chore(lint): baseline root ESLint config + root lint script wired into CI (#16)

eslint.config.js

@@ -1,5 +1,13 @@
 import { defineConfig } from "eslint/config";
 
+// Root ESLint config.
+//
+// Scope: this config only lints repository-root JavaScript (config files,
+// helper scripts). Each sub-package (backend/, frontend/, contract/) owns and
+// runs its own lint setup, so they are ignored here to avoid double-linting
+// with a weaker root ruleset. The baseline below is intentionally dependency
+// free (no @eslint/js / globals packages) so `pnpm run lint` works at the root
+// with only the already-installed `eslint` package and no lockfile changes.
 const eslintConfig = defineConfig([
   {
     ignores: [
@@ -10,8 +18,34 @@ const eslintConfig = defineConfig([
       "**/dist/**",
       "**/target/**",
       "**/.git/**",
+      // Sub-packages have their own ESLint configs and CI lint steps.
+      "backend/**",
+      "frontend/**",
+      "contract/**",
     ],
   },
+  {
+    files: ["**/*.{js,mjs,cjs}"],
+    languageOptions: {
+      ecmaVersion: "latest",
+      sourceType: "module",
+      globals: {
+        process: "readonly",
+        console: "readonly",
+        module: "readonly",
+        require: "readonly",
+        __dirname: "readonly",
+        __filename: "readonly",
+      },
+    },
+    rules: {
+      "no-unused-vars": "error",
+      "no-undef": "error",
+      "no-var": "error",
+      "prefer-const": "error",
+      eqeqeq: ["error", "always"],
+    },
+  },
 ]);
 
 export default eslintConfig;

package.json

@@ -1,7 +1,7 @@
 {
   "private": true,
   "scripts": {
-    "lint": "pnpm --recursive --stream lint",
+    "lint": "eslint .",
     "test": "pnpm --recursive --stream test",
     "build": "pnpm --recursive --stream build",
     "prepare": "husky install",