Stats for one workflow step — the numbers the workflow builder shows under it. Every step
type reports contacts: how many are at the step right now and how many left it inside
the window. A send_email_step also reports email: engagement and attributed revenue
for the email it sends. For every other step type email is null, so a delay or tag
step never reads as an email that performed badly.

contacts.are_here is current occupancy — runs whose current step is this one — and is
the one number that does not follow timerange. contacts.were_here counts contacts who
left the step inside the window, once per pass through it.

Unlike a broadcast, a workflow step has no audience and no send window: it keeps
sending for as long as the workflow runs and contacts keep reaching it. So there is
nothing to report as queued or in progress, and the numbers are always for a window
you choose. Defaults to a 30-day window ending now. Override with timerange_start
and timerange_end. Values are clamped: a future end date is clamped to now, a window
over 90 days is clamped to 90 days, and a start after the end resets to 30 days ending
at timerange_end. Read timerange back from the response for the window actually used.

sends counts a contact once per pass through the step, so a looping workflow makes it
larger than recipients. Rates are whole percentages rounded to the nearest integer — a
share under 0.5% reads 0 next to a non-zero count, and the counts are authoritative.
open_rate, click_rate, bounce_rate and unsubscribe_rate divide by recipients;
click_to_open_rate divides unique clicks by unique opens. The workflow builder's
percentages under a step divide by sends instead, so for a step that sent to a contact
more than once the app shows a lower rate than this endpoint does for the same window;
the counts are the same on both. Numerator and denominator are
each counted inside the window on their own: an open inside the window counts even when
the send it answers happened before the window. So a rate can exceed 100 when few new
sends meet many opens of older emails, and it is 0 whenever its denominator is 0, however
many opens there were. A step whose email last sent before the window reports zero
sends and recipients while opens and clicks inside it still count. To compare like
with like, widen the window to cover the sends you care about.

Revenue is attributed when the buyer's last tracked source within 30 days was a click on
one of the email's links. Each attributed order contributes its first paid invoice,
and only when that invoice was issued inside the window: renewals never count, and an
order whose first payment predates the window contributes nothing even if a renewal was
paid inside it. Only live-mode orders paid in the workspace currency are counted. Note
the engagement counts do include test-mode sends, so the revenue-per-X figures divide
live-only money by counts that may include test traffic.

The broadcast equivalent is GET /emails/broadcasts/{broadcast_id}/stats. Its
performance and revenue blocks share this vocabulary at the top level, with
delivered in place of sends/recipients/failed, and it takes no timerange — a
broadcast reports on its own send window.