Per-layer events gave no sense of how much is LEFT. Downloading lines
are parsed per-layer and summed; every 3s the snapshot becomes
'⏳ 3.14/9.27 GB (34%) · 最大层 3f4a2b1c9d0e: 0.51/1.2 GB' instead of
a bare layer line. Key events (Pulling from / Status / errors) still
print immediately.
Co-ached-By: Claude <noreply@anthropic.com>