json cli [music scrolll + parts] export into audio [mp3, wav]

Your idea

When working with a set / a compilation of music scrolls at some point I want to:

• export the music scores,
• as well as their parts,
• in a self-defined structure
  using a cli batch mode / .json file.

As of the current version 4.6.5 of MuseScore, these the cli .json export is rather limited.

Problem to be solved

Currently: pdf, mxl, and mid exports work fine. But not .mp3, or .wav.

Here's an example of a .json structure:

[
    {
        "in": "myScore1.mscz",
        "out": [
            "./pdfs/myScore1.pdf",
            "./mxls/myScore1.mxl",
            "./audio/myScore1.mid",
            "./audio/myScore1.mp3",
            ["./pdfs/parts/myScore1 (", " part).pdf"]
        ]
    },
    {
        "in": "myScore2.mscz",
        "out": [
            "./pdfs/myScore2.pdf",
            "./mxls/myScore2.mxl",
           "./audio/myScore2.mp3",
            ["./pdfs/parts/myScore2 (", " part).pdf"]
        ]
    }
]

Another, thing that is missing in the .json cli is, to export the audio parts as well. So sth like:

[
    {
        "in": "myScore1.mscz",
        "out": [
            "./pdfs/myScore1.pdf",
            "./mxls/myScore1.mxl",
            "./audio/myScore1.mid",
            "./audio/myScore1.mp3",
            ["./pdfs/parts/myScore1 (", " part).mp3"]
        ]
    },
    {
        "in": "myScore2.mscz",
        "out": [
            "./pdfs/myScore2.pdf",
            "./mxls/myScore2.mxl",
           "./audio/myScore2.mp3",
            ["./pdfs/parts/myScore1 (", " part).mp3"]
        ]
    }
]

And finally, I would be great if one could simplify the syntax of the parts in the json:
["./pdfs/parts/myScore7 (", " part).pdf"]

Ideally this could simply look for example like:
"./pdfs/parts/myScore7 ($PART).pdf"

Prior art

No response

Additional context

No response

Checklist

• This request follows the guidelines for reporting issues
• I have verified that this feature request has not been logged before, by searching the issue tracker for similar requests

Start at MuseScore's CLI JSON batch export entry point and compare how PDF, MXL, and MIDI outputs are handled. Identify the existing audio and parts-export paths, then determine tests for MP3/WAV scores and parts plus the proposed $PART syntax; the work is done when these outputs work in batch mode with the requested structure.