Christian Byrne b2f848893a test: add perf test for viewport pan sweep GC churn (#10479) ...

## Summary

Adds a `@perf` test to establish a baseline for viewport panning GC
churn on large graphs.

## Changes

- **What**: New `large graph viewport pan sweep` perf test that pans
aggressively back and forth across a 245-node graph, forcing many nodes
to cross the viewport boundary. Measures style recalcs, forced layouts,
task duration, heap delta, and DOM node count.

## Review Focus

This is **PR 1 of 2** (perf-fix-with-proof pattern). The fix (viewport
culling) will follow in a separate PR once this baseline is established
on main. CI will then show the delta proving the improvement.

The test uses 120 steps out + 120 steps back at 8px/step = ~960px total
displacement, enough to sweep across a significant portion of the large
graph layout.

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10479-test-add-perf-test-for-viewport-pan-sweep-GC-churn-32d6d73d365081cc9f15fe3d5890675d)
by [Unito](https://www.unito.io)

2026-03-28 13:54:26 -07:00

13 KiB

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