Windows: Closing the installer loader doesn't terminate an aria2c download which is in progress

As per the title, if you close the installer loader (which should terminate the whole installer), it doesn't terminate the aria2c download. This is pretty bad, as it could result in both the download continuing when you don't expect it to, and also multiple aria2c downloads occurring simultaneously.

when running normally:


After closing the installer loader ("07th-mod Installer Launcher [v1.1.47]"):


- [x] make sure when the installer loader GUI is terminated ("07th-mod Installer Launcher [v1.1.47]") the whole proccess is terminated
- [ ] double check the same doesn't happen with 7-zip extraction
- [ ] double check that on other platforms, when the python script is run by itself without a loader, this can't happen (on windows, this seems to work if you run the installer just from the python script)
- [ ] Add actual button to stop the download/extraction on the web UI
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Edit: It looks like this issue has to do with the process being run with a (hidden) console. If you run the process with a console, it's not fully terminated until the console is killed. But we hide the console so as not to confuse users. This seems to make windows keep aria2c alive, as it sees the console window is still there.

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Edit2: after trying out some things, I'm going to try this: https://stackoverflow.com/questions/23434842/python-how-to-kill-child-processes-when-parent-dies/23587108 . It's windows (or linux) specific, but at this stage I just want it to work.

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Edit3: Registering a JobObject at the rust loader using this handy library: https://github.com/ohadravid/win32job-rs seems to fix the issue, but I'll just make sure everything is in order before I release a fix.

The issue is about a Windows-specific process termination problem where aria2c continues after the installer loader GUI closes. The fix involves using a JobObject via the win32job-rs Rust library to ensure child processes are killed. Start by examining the Rust loader code that spawns aria2c, then integrate the JobObject registration. Test by running the installer, closing the loader, and verifying that aria2c processes terminate.

Written by the indexing model from the issue text.