fix(test): update ESLint config for test/unit/ directory

Add test/unit/*.mts to allowDefaultProject in ESLint config to recognize
test files after reorganization into test/unit/ subdirectory.

- Fixes ESLint parsing errors for moved test files
- All 451 tests now pass with proper linting
- Enables proper TypeScript type checking in test files

Author: jdalton

.config/eslint.config.mjs

@@ -240,6 +240,7 @@ export default [
             '.config/*.config.isolated.mts',
             '*.config.mts',
             'test/*.mts',
+            'test/unit/*.mts',
             'test/utils/*.mts',
             'src/*.mts',
           ],