bug: mb pull coder-arm64 fails with corrupt stream, did not find end of stream

[BekahHW]

Description

Attempting to pull the coder-arm64 mixtape fails during the decompression step with a zstd stream error.

The download begins successfully but fails while writing stereos.img.

Steps to Repoduce

mb pull coder-arm64

See Error:

Selected raw disk format from index
Downloading stereos.img.zst (717.6 MiB) -> decompressing to stereos.img
✗ decompressing stereos.img.zst: writing /Users/bekahhw/.config/mb/mixtapes/coder-arm64/latest/stereos.img: corrupt stream, did not find end of stream

After the failure, the directory ~/.config/mb/mixtapes/coder-arm64/latest does not exist

Environment

•	macOS (Apple Silicon)
•	mb version: v0.1.1

Troubleshooting Already Attempted

•	Verified disk space
•	Retried the pull multiple times
•	Confirmed the failure is deterministic
•	Verified mb installation and PATH
•	Checked that no leftover cache directory exists after failure

[linear]

PCC-242