closing tab while in debugger mode incorrectly persists 'deletable' prop on blocks

[jwunderl]

Describe the bug A clear and concise description of what the bug is.

To Reproduce Steps to reproduce the behavior:

1. Go to arcade
2. open any project
3. open debug mode
4. close tab while in debug mode
5. open arcade again and reopen that project
6. right click on any block
7. see missing duplicate block / delete block opts

share link with that state here: https://makecode.com/_KTugcR8rD4jD

Expected behavior

closing tab while in debug mode should not persist debug mode-specific state in the project.

Screenshots

All the blocks get the deletable="false" prop added to them:

Additional context

reported by user on forum https://forum.makecode.com/t/missing-context-menu-items-duplicate-and-delete-block-s/14729