When the patch tool matches via the escape_normalized strategy, old_string
contains literal \t, \n, \r sequences that get unescaped to match real
control characters in the file. However, new_string was written as-is,
leaving literal backslash sequences in the output.
Add _unescape_common_sequences() helper and apply it to new_string when
the matching strategy is escape_normalized. This ensures LLM-generated
tab/newline sequences become real bytes in the patched file.
Fixes#33733
e9f3f2b34a