tests: fix ruff/pre-commit issues in test_replace_cow_fix; normalize FINAL_REPORT.md line endings

Author: Mayank

FINAL_REPORT.md

@@ -51,7 +51,7 @@ self_blk_ids = {
 
 **The Issue:**
 1. `b()` calls could return `None` if weak references became invalid
-2. `id(None)` would be used as a key, causing later KeyError 
+2. `id(None)` would be used as a key, causing later KeyError
 3. The error manifested as "weakref is not in list" when trying to pop from the list
 
 ### Why np.nan specifically?
@@ -212,4 +212,4 @@ This fix successfully resolves the pandas CoW DataFrame.replace bug by implement
 **Fix completed by:** Assistant  
 **Date:** 2025-10-22  
 **Validation:** ✅ All tests pass  
-**Deployment:** ✅ Ready for production
+**Deployment:** ✅ Ready for production