[popups] Fix disabled anchor tracking on scroll

[atomiks]

Fixes #5405

disableAnchorTracking still subscribed to overflow-ancestor scroll events, so popups followed their anchor during scrolling even though element resize and layout-shift tracking were disabled. The ancestorScroll option was dropped in #1249 during an unrelated refactor.

This restores the original behavior while leaving ancestorResize enabled for resize updates.

Changes

• Disable overflow-ancestor scroll updates when anchor tracking is disabled.
• Add Chromium regression coverage that scrolls an overflow ancestor and verifies the popup remains in its initial position.

[pkg-pr-new]

• base-ui-tanstack-start

• vite-css-base-ui-example

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/react@5478
  

  pnpm add https://pkg.pr.new/mui/base-ui/@base-ui/utils@5478
  

commit: 7a04b35

[code-infra-dashboard]

Bundle size

Bundle	Parsed size	Gzip size
@base-ui/react	🔺+18B(0.00%)	🔺+10B(+0.01%)

Details of bundle changes

Performance

Total duration: 1,382.89 ms +3.01 ms^(+0.2%) | Renders: 76 ⁽⁺⁰⁾ | Paint: 2,157.69 ms +30.13 ms^(+1.4%)

Test	Duration	Renders
Menu mount (300 instances)	124.29 ms 🔺+24.40 ms(+24.4%)	1 (+0)

14 tests within noise — details

Metric alarms

Test	Metric	Change
Menu mount (300 instances)	bench:paint	🔺 +35.04 ms

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