Bump Next.js and drop ESLint (#19898)

This PR bumps Next.js and drops ESLint. 

We only had ESLint installed because it came with `next lint`. We don't
actively use ESLint, it was just used in the playgrounds where we test
things out. Dropping this reduces the amount of dependencies we have to
deal with.

Closes: #19867
Closes: #19852

# Test plan

Tested both the `nextjs` and `v3` playgrounds after bumping the Next.js
dependency and getting rid of ESLint, and they still work as expected.

playgrounds/nextjs/app/page.module.css

@@ -1,5 +1,5 @@
 @reference "./globals.css";
 
 .heading {
-  @apply skew-7;
+  @apply text-red-500;
 }

playgrounds/nextjs/package.json

@@ -5,23 +5,26 @@
   "scripts": {
     "dev": "next dev",
     "build": "next build",
-    "start": "next start",
-    "lint": "next lint"
+    "start": "next start"
   },
   "dependencies": {
     "@tailwindcss/postcss": "workspace:^",
     "fast-glob": "^3.3.3",
-    "next": "^16.1.6",
-    "react": "^19.2.4",
-    "react-dom": "^19.2.4",
+    "next": "16.2.2",
+    "react": "19.2.4",
+    "react-dom": "19.2.4",
     "tailwindcss": "workspace:^"
   },
   "devDependencies": {
     "@types/node": "catalog:",
-    "@types/react": "^19.2.14",
-    "@types/react-dom": "^19.2.3",
-    "eslint": "^9.39.2",
-    "eslint-config-next": "^16.1.6",
+    "@types/react": "19.2.14",
+    "@types/react-dom": "19.2.3",
     "typescript": "^5.9.3"
+  },
+  "pnpm": {
+    "overrides": {
+      "@types/react": "19.2.14",
+      "@types/react-dom": "19.2.3"
+    }
   }
 }

playgrounds/nextjs/tsconfig.json

@@ -10,7 +10,7 @@
     "moduleResolution": "bundler",
     "resolveJsonModule": true,
     "isolatedModules": true,
-    "jsx": "preserve",
+    "jsx": "react-jsx",
     "incremental": true,
     "plugins": [
       {
@@ -20,7 +20,14 @@
     "paths": {
       "@/*": ["./*"],
     },
+    "target": "ES2017",
   },
-  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts",
+  ],
   "exclude": ["node_modules"],
 }

playgrounds/v3/package.json

@@ -9,18 +9,22 @@
     "upgrade": "node scripts/upgrade.mjs"
   },
   "dependencies": {
-    "next": "^16.1.6",
-    "react": "^19.2.4",
-    "react-dom": "^19.2.4",
+    "next": "16.2.2",
+    "react": "19.2.4",
+    "react-dom": "19.2.4",
     "tailwindcss": "^3"
   },
   "devDependencies": {
     "@types/node": "catalog:",
-    "@types/react": "^19.2.14",
-    "@types/react-dom": "^19.2.3",
+    "@types/react": "19.2.14",
+    "@types/react-dom": "19.2.3",
     "autoprefixer": "^10.4.24",
-    "eslint": "^9.39.2",
-    "eslint-config-next": "^16.1.6",
     "typescript": "^5.9.3"
+  },
+  "pnpm": {
+    "overrides": {
+      "@types/react": "19.2.14",
+      "@types/react-dom": "19.2.3"
+    }
   }
 }

playgrounds/v3/tsconfig.json

@@ -10,7 +10,7 @@
     "moduleResolution": "bundler",
     "resolveJsonModule": true,
     "isolatedModules": true,
-    "jsx": "preserve",
+    "jsx": "react-jsx",
     "incremental": true,
     "plugins": [
       {
@@ -20,7 +20,14 @@
     "paths": {
       "@/*": ["./*"],
     },
+    "target": "ES2017",
   },
-  "include": ["next-env.d.ts", "**/*.ts", "**/*.tsx", ".next/types/**/*.ts"],
+  "include": [
+    "next-env.d.ts",
+    "**/*.ts",
+    "**/*.tsx",
+    ".next/types/**/*.ts",
+    ".next/dev/types/**/*.ts",
+  ],
   "exclude": ["node_modules"],
 }