Previously, the workspace "Download logs" dialog formatted the original byte
count with the promoted unit, so sizes above 1 KiB could be shown incorrectly,
for example 4472 KB instead of 4.37 KB. Exact 1024-byte files also stayed
in bytes.

Update humanBlobSize to format the scaled value correctly, promote 1024 B
to 1 KB, and omit trailing .00 for whole numbers. Export the helper and add
a focused regression test covering bytes, the KiB boundary, fractional KiB, and
MiB cases.

Before	After