fix(tsconfig): include root config files for type checking

playwright.config.ts などのルート直下の .config.ts ファイルを
TypeScript の型チェック対象に含める。これにより process グローバルが認識される。

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Author: KATO-Hiro

tsconfig.json

@@ -20,6 +20,6 @@
   //
   // If you want to overwrite includes/excludes, make sure to copy over the relevant includes/excludes
   // from the referenced tsconfig.json - TypeScript does not merge them in
-  "include": ["src/**/*.d.ts", "src/*", "src/**/*.ts", "src/**/*.svelte", "prisma/**/*.ts"],
+  "include": ["src/**/*.d.ts", "src/*", "src/**/*.ts", "src/**/*.svelte", "prisma/**/*.ts", "*.config.ts"],
   "exclude": [".git", "node_modules"]
 }