formatElapsedSeconds rounded every duration to one decimal, so calls
under 50 ms rendered as 0 s. Durations below one second now show integer
milliseconds (29 ms); at or above one second the tenth-of-a-second label
is unchanged (1.5 s). Step group descriptions reuse the same formatter.
The details-panel Duration rows toggle between the readable label and
exact milliseconds on click, mirroring the StartedAt toggle; the shared
text-selection guard is extracted for both. tabular-nums is dropped from
detail values and the toggle buttons because SF's tnum feature widens
the decimal point and leaves excessive space after it.
afb6ee2c9b