Active screen buffer size is out of sync

Nobody has claimed this yet.

### Windows Terminal version

current main branch

### Windows build number

10.0.19045.3448

### Other Software

_No response_

### Steps to reproduce

- Run WT with any profile
- Run the following c++20 code (creates additional screen buffer and make it active)
- Resize the current pane (e.g., split pane)
- Press any key to exit
- Check the current size report - it is not valid
- Run any TUI app just to be sure (e.g. wsl mc )

```cpp
#include
#include

int main()
{
auto len = DWORD{};
auto rec = INPUT_RECORD{};
auto inf = CONSOLE_SCREEN_BUFFER_INFO{};
auto inp = ::GetStdHandle(STD_INPUT_HANDLE);
auto out = ::GetStdHandle(STD_OUTPUT_HANDLE);
auto alt = ::CreateConsoleScreenBuffer(GENERIC_READ | GENERIC_WRITE, 0, 0, CONSOLE_TEXTMODE_BUFFER, 0);
::SetConsoleActiveScreenBuffer(alt);
::GetConsoleScreenBufferInfo(alt, &inf);
auto msg = "current size: " + std::to_string(inf.dwSize.X) + "x" + std::to_string(inf.dwSize.Y)
+ "\nchange pane size and press any key\n";
::WriteFile(alt, msg.data(), msg.size(), &len, 0);
while (true)
{
::ReadConsoleInputW(inp, &rec, 1, &len);
if (rec.EventType == KEY_EVENT && rec.Event.KeyEvent.bKeyDown) break;
else if (rec.EventType == WINDOW_BUFFER_SIZE_EVENT)
{
::GetConsoleScreenBufferInfo(out /*not alt*/, &inf);
msg = "current size: " + std::to_string(inf.dwSize.X) + "x" + std::to_string(inf.dwSize.Y) + "\n";
::WriteFile(alt, msg.data(), msg.size(), &len, 0);
}
}
::SetConsoleActiveScreenBuffer(out);
::GetConsoleScreenBufferInfo(out, &inf);
msg = "current size: " + std::to_string(inf.dwSize.X) + "x" + std::to_string(inf.dwSize.Y) + "\n";
::WriteFile(out, msg.data(), msg.size(), &len, 0);
}
```

### Expected Behavior

After run
```
current size: 106x20
change pane size and press any key
current size: 51x20
```
After exit
```
PS D:\sources\test\size_test\x64\Debug> .\cpp20app.exe
current size: 51x20
PS D:\sources\test\size_test\x64\Debug>
```

### Actual Behavior

After run
```
current size: 106x22
change pane size and press any key
current size: 106x22
```
After exit (the size has not changed despite the pane split!)
```
PS D:\sources\test\size_test\x64\Debug> .\cpp20app.exe
current size: 106x21
PS D:\sources\test\size_test\x64\Debug>
```
wsl mc:

Start by running the provided C++20 reproducer on Windows Terminal with a split-pane resize, then compare the reported screen-buffer dimensions before and after the resize. Check the behavior with a TUI app such as `wsl mc`; done means the active buffer and returned console size reflect the resized pane after the alternate buffer is restored.

Written by the indexing model from the issue text.