fix(ui): make npm run lint actually run

ui/eslint.config.js

@@ -0,0 +1,65 @@
+// ESLint flat configuration.
+//
+// Replaces `.eslintrc.cjs`. ESLint 9 no longer reads the `.eslintrc.*` format
+// and stops with "couldn't find an eslint.config.(js|mjs|cjs) file", so
+// `npm run lint` fails before examining a single source file -- the lint
+// script has been reporting a configuration error rather than passing.
+//
+// A direct translation of the previous configuration: same extends, same
+// rules, same ignores, same React version. Nothing here is an opinion about
+// how this project should be linted; it is the old file expressed in the
+// format the installed ESLint understands.
+import js from "@eslint/js";
+import globals from "globals";
+import react from "eslint-plugin-react";
+import reactHooks from "eslint-plugin-react-hooks";
+import reactRefresh from "eslint-plugin-react-refresh";
+
+export default [
+  { ignores: ["dist/**", "node_modules/**"] },
+  js.configs.recommended,
+  {
+    files: ["**/*.{js,jsx}"],
+    languageOptions: {
+      ecmaVersion: "latest",
+      sourceType: "module",
+      globals: {
+        ...globals.browser,
+        ...globals.es2020,
+      },
+      parserOptions: {
+        ecmaFeatures: { jsx: true },
+      },
+    },
+    settings: { react: { version: "18.2" } },
+    plugins: {
+      react,
+      "react-hooks": reactHooks,
+      "react-refresh": reactRefresh,
+    },
+    rules: {
+      ...react.configs.recommended.rules,
+      // The JSX transform means React need not be in scope.
+      ...react.configs["jsx-runtime"].rules,
+      ...reactHooks.configs.recommended.rules,
+      "react/jsx-no-target-blank": "off",
+      "react-refresh/only-export-components": [
+        "warn",
+        { allowConstantExport: true },
+      ],
+    },
+  },
+  {
+    // Node runs the test files and the build tooling, so they see Node
+    // globals rather than browser ones.
+    files: [
+      "**/*.test.js",
+      "vite.config.js",
+      "*.config.js",
+      "scripts/**/*.js",
+    ],
+    languageOptions: {
+      globals: { ...globals.node },
+    },
+  },
+];

ui/package.json

@@ -48,6 +48,9 @@
   },
   "overrides": {
     "brace-expansion": "^5.0.6",
+    "minimatch@3": {
+      "brace-expansion": "^1.1.18"
+    },
     "tmp": "^0.2.6",
     "shell-quote": "^1.10.0",
     "form-data": "^4.0.6",
@@ -58,6 +61,7 @@
     "@babel/core": "^7.29.6"
   },
   "devDependencies": {
+    "@eslint/js": "^9.39.5",
     "@types/react": "^18.3.3",
     "@types/react-dom": "^18.3.0",
     "@vitejs/plugin-react": "^5.0.0",
@@ -66,6 +70,7 @@
     "eslint-plugin-react": "^7.34.3",
     "eslint-plugin-react-hooks": "^7.0.1",
     "eslint-plugin-react-refresh": "^0.4.7",
+    "globals": "^14.0.0",
     "vite": "^8.0.16",
     "vite-plugin-env-compatible": "^2.0.1"
   }