fix: dir(concurrent.futures) and tab completion broken

[henryiii]

I just noticed that in 3.14rc1, tab completion is broken on concurrent.futures. Trying dir, I got:

>>> import concurrent.futures
>>> dir(concurrent.futures)
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    dir(concurrent.futures)
    ~~~^^^^^^^^^^^^^^^^^^^^
  File "/Users/henryschreiner/.local/share/uv/python/cpython-3.14.0rc1+freethreaded-macos-x86_64-none/lib/python3.14t/concurrent/futures/__init__.py", line 47, in __dir__
    return __all__ + ('__author__', '__doc__')
           ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~
TypeError: can only concatenate list (not "tuple") to list

There's a typo in the __dir__ function; it is trying to concatenate a list and a tuple. I could do [*__all__ , '__author__', '__doc__'] instead if that's preferred.

I didn't make an issue, but I can if that's preferred. Needs backport to 3.14. Also didn't add a test, but a test that checks dir on all modules would be useful. Static typing would have caught this.

Bug introduced in #136381.

[serhiy-storchaka]

Lib/test/test___all__.py may be a good place for the dir() tests.

[ZeroIntensity]

I didn't make an issue, but I can if that's preferred.

I think it'd be a good idea to make an issue, as this should probably be a release blocker.

[henryiii]

Okay, I will when not on an airplane. :)