A 304-frame request sat at "generating 0/16 (0%)" for its whole nine-minute
first segment while the service's log showed Denoising: 15/16. Two defects.

The service set _progress["step"] = 0 at the start of every segment and never
again, so the step count existed only inside the vendored pipeline's
tqdm(total=len(timesteps), desc="Denoising") -- which takes no callback.
Nothing reached GET /progress; the poller in video.py faithfully reported the
0 it was handed. Each pipeline module did `from tqdm import tqdm`, so the bar
is instrumented by rebinding the name on the MODULE (patching tqdm.tqdm would
be too late), and only bars labelled "Denoising" are tracked so a
checkpoint-shard bar cannot move a request's progress.

The totals also counted ONE segment: a four-segment render would have run
0->16 four times against a denominator of 16. `step` now carries the completed
segments' offset so it counts the stage end to end, and the bar spans
steps x segments -- with refinement excluded, being a single pass over the
finished video. A request that asked for a duration rather than a segment
count only learns the real count from the service, so the denominator is
corrected on the first report, through a setter that does not restart the bar
and lose the elapsed time the rate is derived from.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>