ProgressStage declares Resolving and Verifying, and the init, model and
download commands render both, but DownloadManager never emitted either:
the server probe and the integrity finalize / checksum check ran with no
progress event, so those CLI branches were unreachable and a long hash of
a large file looked like a stall.
The manager now reports Resolving before the probe and Verifying before
the digest is finalized. A new test records every stage the manager
emits for a checksummed download and requires Resolving < Connecting <
Verifying < Finalizing; it fails before this change.
Found by pipe's experimental C++ front end: both stages were matched in
CLI switches but never produced anywhere in src/.
9ca69d42a1