Unexpected project data loss caused by saveToCloud under edge cases

[aofei]

Description

The auto-save mechanism introduces an edge case where Project.saveToCloud or Project.saveToLocalCache may run after Project.dispose is called or while Project.history is making changes. This can lead to intermediate state resources (e.g., sprites and sounds) being saved, resulting in data corruption.

Possible solution

Ensure Project.saveToCloud and Project.saveToLocalCache only run when resources are stable by locking Project.history before Project.export and confirming Project isn't disposed before saving.