Restore working lint setup and fix Playwright cold-start flake

.eslintignore

@@ -0,0 +1,4 @@
+dist/
+node_modules/
+playwright-report/
+test-results/

.eslintrc.js

@@ -0,0 +1,74 @@
+module.exports = {
+  root: true,
+  env: {
+    node: true,
+    browser: true,
+  },
+  extends: [
+    'plugin:vue/essential',
+    '@vue/airbnb',
+    '@vue/typescript/recommended',
+  ],
+  parserOptions: {
+    ecmaVersion: 2020,
+  },
+  rules: {
+    'no-console': process.env.NODE_ENV === 'production' ? 'warn' : 'off',
+    'no-debugger': process.env.NODE_ENV === 'production' ? 'warn' : 'off',
+
+    // Git normalizes EOLs on checkout, so working copies are CRLF on Windows
+    // and LF elsewhere. Enforcing either one breaks lint on half the machines.
+    'linebreak-style': 'off',
+
+    'max-len': ['error', {
+      code: 120,
+      ignoreUrls: true,
+      ignoreStrings: true,
+      ignoreTemplateLiterals: true,
+      ignoreRegExpLiterals: true,
+    }],
+
+    // Vue 2 deliberately skips reactivity for keys beginning with `_`.
+    // SelectStep relies on that to hold large track arrays without paying the
+    // cost of making every element reactive, so the prefix is load-bearing.
+    'no-underscore-dangle': 'off',
+
+    // Scrobbling is intentionally sequential: Last.fm rate-limits aggressively
+    // and each request must settle (and its backoff elapse) before the next.
+    'no-await-in-loop': 'off',
+
+    // `new Promise((r) => setTimeout(r, ms))` is the sleep idiom used for
+    // rate-limit backoff throughout the Last.fm client.
+    'no-promise-executor-return': 'off',
+
+    'no-plusplus': 'off',
+    'no-continue': 'off',
+    'class-methods-use-this': 'off',
+
+    // airbnb bans for..of wholesale; it is used throughout for readable
+    // iteration. The genuinely hazardous constructs stay banned.
+    'no-restricted-syntax': ['error', 'ForInStatement', 'LabeledStatement', 'WithStatement'],
+
+    // The base rule flags TypeScript parameter properties as useless
+    // constructors; the TS-aware version understands they declare fields.
+    'no-useless-constructor': 'off',
+    '@typescript-eslint/no-useless-constructor': 'error',
+
+    // Views are legitimately single-word (Home, About, Scrobble, Scrobblify).
+    'vue/multi-word-component-names': 'off',
+
+    // Vuetify data tables address slots with dotted names (`item.artist`),
+    // which the rule reads as modifiers.
+    'vue/valid-v-slot': ['error', { allowModifiers: true }],
+  },
+  overrides: [
+    {
+      // Playwright specs and the dev-mock harness run in Node, not the browser,
+      // and legitimately import from devDependencies.
+      files: ['tests/**/*.{js,ts}', '*.config.js', '.eslintrc.js'],
+      rules: {
+        'import/no-extraneous-dependencies': ['error', { devDependencies: true }],
+      },
+    },
+  ],
+};

.github/workflows/ci.yml

@@ -5,6 +5,19 @@ on:
     branches: [master]
 
 jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 18
+          cache: npm
+      - run: npm ci
+      # --no-fix: `npm run lint` auto-fixes, which would let CI silently pass.
+      - run: npm run lint:check
+
   build:
     name: Build
     runs-on: ubuntu-latest

.github/workflows/pr.yml

@@ -5,6 +5,19 @@ on:
     branches: [master]
 
 jobs:
+  lint:
+    name: Lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 18
+          cache: npm
+      - run: npm ci
+      # --no-fix: `npm run lint` auto-fixes, which would let CI silently pass.
+      - run: npm run lint:check
+
   build:
     name: Build
     runs-on: ubuntu-latest

.postcssrc.js

@@ -1,5 +1,5 @@
 module.exports = {
   plugins: {
-    autoprefixer: {}
-  }
-}
+    autoprefixer: {},
+  },
+};

AGENTS.md

@@ -71,3 +71,18 @@ Network failures emit `scrobble_network_error`.
 Use the helpers in `src/services/Analytics.ts` (`trackEvent`, `trackError`,
 `identifyUser`) rather than calling `posthog` directly. Analytics must never
 break the app: every call is wrapped in try/catch and ignored on failure.
+
+## Linting
+
+`npm run lint` auto-fixes; `npm run lint:check` (`--no-fix`) is what CI runs, so
+use that to see what CI will see. The config is ESLint + `@vue/airbnb` +
+`@vue/typescript`.
+
+Several airbnb rules are switched off in `.eslintrc.js` because they fight
+patterns this codebase uses on purpose — each has a comment explaining why.
+The load-bearing one: **`no-underscore-dangle` is off because Vue 2 skips
+reactivity for keys starting with `_`**, which is how `SelectStep` holds large
+track arrays cheaply. Renaming those fields would silently make them reactive
+and tank performance on big histories.
+
+Warnings (mostly `no-explicit-any`) do not fail the build; only errors do.

babel.config.js

@@ -1,10 +1,10 @@
 module.exports = {
-  "presets": [
+  presets: [
     [
-      "@vue/app",
+      '@vue/app',
       {
-        "useBuiltIns": "entry"
-      }
-    ]
-  ]
-}
+        useBuiltIns: 'entry',
+      },
+    ],
+  ],
+};