Suppress final live render for non-interactive output

[praneetware]

Related issue: #3040

Description

This draft PR explores a possible fix for issue #3040 ("Interactive progress bars are being written to files").

Reproduction

Using the following example:

from rich.progress import track
from time import sleep

for _ in track(range(10), description="Doing stuff"):
    sleep(0.1)

and redirecting stdout:

python repro.py > output.txt

the resulting file contains:

Doing stuff ---------------------------------------- 100% 0:00:01

Investigation

While investigating, I found that Live.process_renderables() explicitly renders the final live output for non-interactive outputs:

elif (
    not self._started and not self.transient
):
    renderables = [*renderables, self._live_render]

The documentation states that Rich removes animations such as progress bars when not writing to a terminal, so I wanted to explore whether the final rendered progress output should also be suppressed.

Change

This draft removes the final live render for non-interactive outputs, which prevents progress bars from being written to redirected output files.

Notes

This is submitted as a draft PR to gather feedback on the intended behavior before adding tests or making further changes.