orig/Celeste.exe is coreified and does not run

[SnipUndercover]

My mods and Everest install are up to date

Yes

I have recreated the bug with only Everest OR a minimum number of mods enabled

Yes

Describe the bug

If the installation of Everest fails after coreification but before the apphost setup, the next install will cause Olympus to delete the orig directory under the assumption that this is a vanilla install and safe to backup.
This causes the vanilla executable in orig/Celeste.exe to be coreified. Trying to run coreified vanilla will always crash with this message in the Event Viewer on Windows:

Application: Celeste.exe
Framework Version: v4.0.30319
Description: The process was terminated due to an unhandled exception.
Exception Info: exception code e0434352, exception address 00007FF9899C7F7A
Stack:

Steps to reproduce

1. Try to install Everest
2. Have the install fail after coreification but before the apphost setup (so before or while running MonoMod)
3. Install Everest from Olympus
4. orig/Celeste.exe is coreified

Expected behavior

orig/Celeste.exe remains a .NET Framework assembly and runs normally.

Operating System

N/A (OS-agnostic)

Everest Version

5800, but likely applies to all core (4465+) versions

Mods required to reproduce

No response

Additional context

Since MiniInstaller does not do any cleanup if installation fails, Celeste.exe is converted to .NET Core without applying any of the Everest patches. Then, when installing from Olympus, it finds that Celeste.exe is vanilla (unaware of the fact that it's coreified), and deletes orig under the oblivious assumption that this is a vanilla install and safe to back up.

The deletion logic can be found in Olympus' CmdInstallEverest.

[SnipUndercover]

When updating Everest from inside Everest on Windows, people are getting a black console window with no output when MiniInstaller is run (since its output is redirected).
Since running MonoMod is the operation taking the longest to finish, there is a very wide window of time where end users can do end user things (close the console window, since it's doing "nothing"). This cuts the update off mid-way in the exact conditions required for this issue to surface.

The natural next course of action would be to retry the update from Olympus, which makes orig/Celeste.exe coreified.