blobs, store and portable each built a BlobStore in a temp directory their own
way: pid+tag twice, a uuid once. blobs::scratch(tag) is that, with a counter, so
two tests can never share a directory even if they pick the same tag. The
desktop's and ffi's temp-dir helpers stay, one per crate: sharing them would
need a test-util feature on the core crate.
DRY pass #2, batch 2, F9 (#5372).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
bvandeusenandClaude Opus 5.5
2dec89bf8c