Renderer always subtracts one from the terminal width, leaving a column unoccupied

https://github.com/prompt-toolkit/python-prompt-toolkit/blob/5b3dd6dbbd72ac8323e749cc12e6aa2d7c7411af/src/prompt_toolkit/renderer.py#L199-L200

The renderer always subtracts one from the terminal width, leaving a column on the right unoccupied. This is a column that the application could be using (and seemingly has no reason to avoid), and looks ugly.

This monkey-patch seems to work perfectly fine, for fullscreen and non-fullscreen applications:

		old_get_size = app.output.get_size

		def new_get_size():
			size = old_get_size()
			return Size(size.rows, size.columns + 1)

		app.output.get_size = new_get_size

Perhaps prompt-toolkit used to rely on some cursor positioning detail that required a workaround, but that doesn't seem to be the case anymore. I propose simply removing the - 1 altogether. Is there even any reason to keep it?

Start in src/prompt_toolkit/renderer.py at lines 199-200 and inspect why one column is subtracted from the terminal width. Reproduce the behavior in fullscreen and non-fullscreen applications, then verify that removing the subtraction uses the final terminal column without breaking cursor positioning.