The chart benchmark warmed its response cache and then timed a fresh
payload-retaining recorder. That hid store-backed work behind test buffer
allocation and made the regression signal ambiguous.
Measure cached handler work, fresh-service computation and real loopback
HTTP transfer separately. Wait for store startup maintenance, preserve the
original failed comparison and record the paired diagnostic limits. Make
the adjacent SLO exercise uncached chart generation at its existing budget.
Refs #3052
rcourtman
c369bf3076