If the editor is not closed gracefully the `ModToolStore` is not saved to disk

https://github.com/GodotModding/godot-mod-tool/blob/63e2e4cf108083494c545f3904ee5a78ee9d2bcd/addons/mod_tool/global/store.gd#L46-L48

`_exit_tree()` is not called if the editor crashes. This happens quite often when the editor is restarted via *Project* -> *Reload Current Project*.

Start by reading addons/mod_tool/global/store.gd around lines 46-48 and inspect how ModToolStore is currently saved from _exit_tree(). Investigate what happens during Project → Reload Current Project, then define a persistence path that still saves the store when the editor does not close gracefully. Done means the store is saved to disk in that scenario.

Written by the indexing model from the issue text.