The previous parser walked `-X importtime` stderr by hand (string-splitting
on `|`, indent-width math). Replace it with a load of the HAR JSON that
importtime-waterfall already produces: each entry carries the module name,
self-time, and cumulative — no tree reconstruction needed. Drops the
hand-rolled retry loop too, since importtime-waterfall does best-of-6
internally.
The committed budget (75.2ms) was seeded on a fast local machine; GHA
runners measured 122.8ms, so the first CI run tripped the check. Reset
the baseline to 123ms with a 25% margin (ceiling ~154ms) to absorb GHA
variance. Tighten later once we have several data points.
Adds unit tests for should_run_import_time across the trigger matrix and
wires the new mock into the existing test_main_* suite.
J. Nick Koston
900232be21