Surface focused acquisition worker failures without waiting for other downloads #445

The focused Sid controller waits on futures in source order inside a ProcessPoolExecutor context. The selected bulk TPST1::CRCP reconstruction reproduced #438 immediately, but its traceback was withheld while the context waited for unrelated ONT downloads and the remaining sources. This hid the actual blocker for tens of minutes.

Observe completed futures and stop only this CLI's owned workers before propagating any controller/worker failure. Preserve completed acquisition checkpoints and leave interrupted targets pending, without publishing empty counts. Extend the cancellation regression and verify a real worker failure terminates the controller promptly.

Related: #433, #438, #443. #444 fixes the original record-identity error separately.