Hey Terry, after testing the committed patch on my Linux Mint, I have found the following behaviour:

1. The issue of IDLE not starting when Recent File list has name outside BMP has been fixed.

2. The File Name is correctly formatted and displayed in the file editor window title and in the recent file list.(astral chars replaced by diamond question mark symbol)

3. Files with astral char names now RUN perfectly.

4. You can create a file with astral char in its name and run it effectively and re run it from the recent file list.

PS : since you are unable to test it own windows and many other developers might face the same I'm uploading the screenshot of the IDLE windows after the patch is applied.
In the given test , I had kept my file name as "𝔼𝔼hello𝒵My𝔼Name𝒫.py"
and it was displayed as "��hello�My�Name�.py"