ci: add pull request quality gates

Co-Authored-By: gpt-5.6-terra <noreply@openai.com>

package.json

@@ -25,7 +25,9 @@
     "test:shared": "node --import tsx/esm --import ./src/meta/dev/register.ts --test $(find test/backends -name 'index.test.ts' | sort)",
     "test:tools": "node --import tsx/esm --import ./src/meta/dev/register.ts --test $(find test/tools -name '*.test.ts' | sort)",
     "typecheck": "tsc --noEmit",
-    "typecheck:test": "tsc --noEmit -p tsconfig.test.json"
+    "typecheck:test": "tsc --noEmit -p tsconfig.test.json",
+    "lint": "eslint .",
+    "format:check": "prettier --check ."
   },
   "dependencies": {
     "@koa/bodyparser": "^6.0.0",
@@ -44,21 +46,25 @@
     "react-redux": "^9.2.0"
   },
   "devDependencies": {
+    "@eslint/js": "^9.39.5",
     "@types/better-sqlite3": "^7.6.13",
-    "@types/pg": "^8.20.0",
     "@types/koa": "^3.0.0",
     "@types/koa__router": "^12.0.4",
+    "@types/pg": "^8.20.0",
     "@types/react": "^19.1.12",
     "@types/webpack-bundle-analyzer": "^4.7.0",
     "copy-webpack-plugin": "^13.0.1",
     "css-loader": "^7.1.2",
     "dynohot": "^2.1.1",
+    "eslint": "^9.39.5",
     "mini-css-extract-plugin": "^2.9.4",
+    "prettier": "^3.6.2",
     "raw-loader": "^4.0.2",
     "scss-loader": "^0.0.1",
     "ts-loader": "^9.5.4",
     "tsx": "^4.20.5",
     "typescript": "^5.9.2",
+    "typescript-eslint": "^8.65.0",
     "val-loader": "^6.0.0",
     "webpack-bundle-analyzer": "^4.10.2",
     "webpack-cli": "^6.0.1"