subprocess.run timeout does not function if shell=True and capture_output=True

Bug report

Bug description:

I am using python 3.12.4 on windows 10 and when calling subprocess.run("powershell", shell=True, capture_output=True, timeout=1) code execution seems to suspend indefinetly as the process now accepts the user input and interprets it.

This behaviour matches the one described in #81605 despite it having supposedly been fixed 5 years ago.
For example when calling subprocess.run("cmd", shell=True, capture_output=True, timeout=1) and then entering echo o>f.txt a new file called "f.txt" gets created with "o" as its content.

When using the IDLE Shell the process completes nearly instandly and returns this:

CompletedProcess(args='powershell', returncode=0, stdout=b'Windows PowerShell\r\nCopyright (C) Microsoft Corporation. Alle Rechte vorbehalten.\r\n\r\nLernen Sie das neue plattform\x81bergreifende PowerShell kennen - https://aka.ms/pscore6\r\n\r\nPS C:\Users\Mabeeck\Desktop\Python> ', stderr=b'')

The same applies for Python 3.8.9, 3.9.2, 3.10.6, 3.11.5 and 3.13.0b3
I'll apoligise in advance, if my impression of the bug beeing supposed to be fixed is wrong.

CPython versions tested on:

3.8, 3.9, 3.10, 3.11, 3.12, 3.13

Operating systems tested on:

Windows

Comienza con el punto de entrada subprocess.run usando shell=True, capture_output=True y timeout=1 en Windows, reproduciendo los casos de powershell y cmd reportados. Compara el comportamiento entre las versiones de Python indicadas y determina qué comportamiento de timeout debería producirse cuando el proceso hijo acepta entrada; el issue estará completo cuando se resuelva la suspensión indefinida y el comportamiento quede cubierto por una prueba de regresión adecuada.