Every retained bar carried `animate-lc-bar-in`, so the chart's mount animated
each one — the host retains up to maxRequestSteps (1500) requests — and every
animating bar layerizes on its own. Only the columns a pane can reach are ever
seen: the chart mounts anchored to the newest bars, so the rise is now drawn by
the newest RISE_CAP (200) columns, the stagger counted from the window's edge
so those columns still cascade left to right. Bars appended to a live session
keep rising, and a log shorter than the window is unchanged.
Measured on the 218-step session, the per-bar animations cost 17ms of the worst
frame gap and 16ms of blocking on top of the strip fix. With both changes the
open measures 243 animations, a 133ms worst frame gap (was 250ms) and 98ms of
blocking (was 173ms); with every CSS animation disabled it measures the same
133ms, so what remains is plain mount cost. Three tests pin the window in
total, DNA and DNA+delta modes.
bowenliang123
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