CRLF in multiline headers adds an extra blank row #488

A header containing Windows-style CRLF (\r\n) renders with an extra blank header row. The same header with LF renders as two lines.

Reproduced on current main (268615a5c27dc40e5c22454c07b44d5c50410da0) with CPython 3.14.8 on Windows:

from tabulate import tabulate

print(tabulate([[1]], headers=['A\nB'], tablefmt='grid'))
print(tabulate([[1]], headers=['A\r\nB'], tablefmt='grid'))

The LF header renders as:

+-----+
|   A |
|   B |
+=====+
|   1 |
+-----+

The CRLF header instead renders as:

+-----+
|   A |
|     |
|   B |
+=====+
|   1 |
+-----+

Expected: CRLF and LF represent one line break and produce the same two-line header. A data cell containing A\r\nB renders as two lines, so this appears specific to header alignment.

_align_header splits using _multiline_codes = re.compile(r'\r|\n|\r\n'); the \r alternative consumes the first half of a CRLF before the \r\n alternative can match.