Resolve build process errors

Run the build and fix the errors

The build still fails. Let me check the actual error more carefully:

No, don't change it to a var. Recreate the full structure.
Ran tool undo_edit
Explored 2 files
Edited AppDelegate.swift
+6
-2
Ran tool todo_write
Ran tool todo_write

Build successful! Fixed the error by recreating the Downloading struct with updated values instead of mutating it.