refactor: use targeted ESLint override for test files only

- Removed global @typescript-eslint/no-unused-expressions: off
- Kept the rule enabled for main codebase (better code quality)
- Only disabled the rule for test/**/*.ts files where expect statements are expected
- More precise and maintainable ESLint configuration

Author: jamesvillarrubia

.eslintrc.json

@@ -34,8 +34,7 @@
     ],
     "@typescript-eslint/no-unused-vars": "off",
     "@typescript-eslint/no-explicit-any": "off",
-    "no-unused-expressions": "off",
-    "@typescript-eslint/no-unused-expressions": "off"
+    "no-unused-expressions": "off"
   },
   "overrides": [
     {