build: normalize filepath slashes, eol consistency #6353

## Problem
- Tests were failing or behaving inconsistently on different operating
systems due to improper file path normalization.
- End-of-line (EOL) conflicts were causing unnecessary formatting diffs
in collaborative workflows.

## Solution
- Updated the testFile variable in the test runner to normalize paths by
replacing backslashes (\) with forward slashes, ensuring cross-platform
compatibility.
- Added the Prettier rule 'prettier/prettier': ['error', { endOfLine:
'auto' }] to align EOL behavior with the host environment, avoiding
platform-specific conflicts.

Author: muaydin

.eslintrc.js

@@ -209,5 +209,7 @@ module.exports = {
                 ],
             },
         ],
+
+        'prettier/prettier': ['error', { endOfLine: 'auto' }],
     },
 }

packages/core/src/test/testRunner.ts

@@ -84,7 +84,8 @@ export async function runTests(
     })
 
     const dist = path.resolve(root, 'dist')
-    const testFile = process.env['TEST_FILE']?.replace('.ts', '.js')
+    const rawTestFile = process.env['TEST_FILE']
+    const testFile = rawTestFile?.replace(/\\/g, '/').replace('.ts', '.js')
     let testFilePath: string | undefined
     if (testFile?.includes('../core/')) {
         testFilePath = path.resolve(root, testFile.replace('../core/', '../core/dist/'))