Support for Python 3.14

Nobody has claimed this yet.

Thank you very much for your package which works great on my Python 3.13.5:

````cmd
(base) C:\Users\Akira>python -V
Python 3.13.5

(base) C:\Users\Akira>pip show zstandard
Name: zstandard
Version: 0.25.0
Summary: Zstandard bindings for Python
Home-page: https://github.com/indygreg/python-zstandard
Author:
Author-email: Gregory Szorc
License-Expression: BSD-3-Clause
Location: C:\Users\Akira\anaconda3\Lib\site-packages
Requires:
Required-by: conda, conda_index, conda_package_streaming
````

On the other hand, I could not install pgzip on Python 3.14.2:

````cmd
(base) C:\Users\Akira>conda activate myenv

(myenv) C:\Users\Akira>python -V
Python 3.14.2

(myenv) C:\Users\Akira>pip install zstandard
Traceback (most recent call last):
File "C:\Users\Akira\anaconda3\envs\myenv\Scripts\pip-script.py", line 9, in
sys.exit(main())
~~~~^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\cli\main.py", line 65, in main
cmd_name, cmd_args = parse_command(args)
~~~~~~~~~~~~~^^^^^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\cli\main_parser.py", line 79, in parse_command
general_options, args_else = parser.parse_args(args)
~~~~~~~~~~~~~~~~~^^^^^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\optparse.py", line 1361, in parse_args
values = self.get_default_values()
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\cli\parser.py", line 283, in get_default_values
self.config.load()
~~~~~~~~~~~~~~~~^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\configuration.py", line 126, in load
self._load_config_files()
~~~~~~~~~~~~~~~~~~~~~~~^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\configuration.py", line 257, in _load_config_files
config_files = dict(self.iter_config_files())
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\configuration.py", line 352, in iter_config_files
config_files = get_configuration_files()
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\configuration.py", line 72, in get_configuration_files
os.path.join(path, CONFIG_BASENAME) for path in appdirs.site_config_dirs("pip")
~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_internal\utils\appdirs.py", line 47, in site_config_dirs
dirval = _appdirs.site_config_dir(appname, appauthor=False, multipath=True)
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_vendor\platformdirs\__init__.py", line 146, in site_config_dir
).site_config_dir
^^^^^^^^^^^^^^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_vendor\platformdirs\windows.py", line 67, in site_config_dir
return self.site_data_dir
^^^^^^^^^^^^^^^^^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_vendor\platformdirs\windows.py", line 56, in site_data_dir
path = os.path.normpath(get_win_folder("CSIDL_COMMON_APPDATA"))
~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
File "C:\Users\Akira\anaconda3\envs\myenv\Lib\site-packages\pip\_vendor\platformdirs\windows.py", line 209, in get_win_folder_from_registry
directory, _ = winreg.QueryValueEx(key, shell_folder_name)
~~~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [WinError 2] The system cannot find the file specified
````

Could you please have a check on this issue?

Start by reproducing the reported `pip install zstandard` failure on Windows with Python 3.14.2 and compare it with the working Python 3.13.5 setup. Determine whether the failure is in package installation or the shown pip/platformdirs traceback; done means the package can be installed successfully on Python 3.14.

Written by the indexing model from the issue text.