`desync tar -i` writes corrupted stores

[sjuxax]

It seems like a recent commit introduced a bug that makes desync tar -i -s /store/ always produce invalid stores (they fail to pass desync verify immediately after creation).

See a full analysis including a weird half-bisect thing at https://www.perplexity.ai/computer/tasks/investigating-desync-tar-verif-ue_G7WveRzyXWEIcUreoQQ.

[folbricht]

oops, sorry about that. This only affected desync tar -i. Fix incoming in #314

[folbricht]

This should be fixed now. Would you be able to confirm? Thanks for reporting the issue

[sjuxax]

Confirmed that it's working as expected now. Thanks!