[Bug]: Session expiration should prevent data loss

### Expected Behavior

Auto-save is the standard behavior these days and I think anything less than that would be a big shock to people. If I worked for 2 hours on a project, went away for lunch, and came back to all my work being gone I would be livid. Put another way, if I was a new customer I think it would make me quit Azure.

I understand there may be technical reasons this is challenging to fix, but AFAIK comparable experiences like GitHub codespaces don't have any data loss, so it's definitely possible (and again...expected by users).

Also discussed by @bamurtaugh in https://github.com/Azure/azure-functions-vscode-web/issues/18

### Actual Behavior

This message implies I lose my work if I don't save or deploy it:


I didn't actually wait the full time to see what happens, but correct me if that assumption is wrong.

### Priority

High (not-working at all)