v0.3.7 — real progress bar (%, ETA, speed)

UX improvement requested by users: replaced the chunky 'rollout N/M' counter with a real tqdm progress bar that shows percentage, elapsed time, ETA, and steps per second across the WHOLE prediction.

Before:
rollout 3/16

After:
predict KLVFFAE: 43%|████▌ | 17234/40000 [00:32<00:42, 532step/s]

No new dependencies (tqdm was already required by torch). Bar auto-disables when stderr is not a TTY, so logs stay clean.

Headline (unchanged): mean canonical Ramachandran JSD 0.196 vs Microsoft Timewarp 0.468 on the 4AA benchmark, ~123K parameters.