MessagesTimeline browser test "keeps the worked-for heading in place when expanded at the bottom" fails on nightly 0.1.7-nightly.20261103.4138 #30398

The test added in #29166 fails on a clean checkout of 115739c (no local changes), 3 of 3 runs on Linux (Chromium via Playwright):

apps/web/src/components/chat/MessagesTimeline.browser.test.tsx > MessagesTimeline work rows > keeps the worked-for heading in place when expanded at the bottom
expected 577 to be close to 473

The heading appears to move by about 104px after expanding at the bottom. It may depend on the viewport or font metrics of the test environment.