fix(core): probe positioned-child limit in getMaxSupportedCssHeight

[ghiscoding]

Apply fix from 6pac repo's

Problem

getMaxSupportedCssHeight() probes the browser's height limit by doubling a div's height and reading it back. On Chromium that read-back survives to 32,000,000px — but Blink separately clamps absolutely-positioned layout at 16,777,214px (2²⁴−2). Since grid rows are absolutely-positioned children of the canvas, any grid whose canvas exceeds ~16.7M px silently misplaces every row past that boundary.

Reproduced on a 1.5M-row grid at the default 25px row height (canvas capped at the probed 32M px):

row 1,499,964:  style.top: 26,703,000px   →   offsetTop: 16,777,214

Every row between ~16.7M and 32M canvas px stacks up at the clamp. At 25px rows this hits any grid beyond ~671k rows; the virtual-paging machinery that exists precisely to avoid the browser limit never engages because the probe reports a limit the browser can't actually position at.

Fix

Probe what the grid actually depends on: alongside the height read-back, position a 1px marker child at top: test - 1 and require marker.offsetTop === test - 1. The probe stops at the first height where either check fails.

On Blink the doubling sequence (1M → 2M → … → 16M → 32M) now fails at the 32M step and returns 16,000,000, safely inside the real limit, so the existing page-switching machinery simply engages earlier. Firefox is unaffected (ffMaxSupportedCssHeight caps the probe at 6M, below the clamp). The options.maxSupportedCssHeight / ffMaxSupportedCssHeight escape hatches are unchanged.

Verification

• Chromium now probes 16,000,000 (was 32,000,000).
• The 1.5M-row repro above renders correctly: for rendered rows at every scroll position, offsetTop equals the requested style.top (paging keeps in-canvas positions under 16M).
• Full Cypress suite passes (grids in the examples are far below the threshold, so no behaviour change for them).

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.0%. Comparing base (a944424) to head (7a919ff).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2645   +/-   ##
=======================================
  Coverage   100.0%   100.0%           
=======================================
  Files         200      200           
  Lines       25317    25320    +3     
  Branches     8951     8951           
=======================================
+ Hits        25317    25320    +3     

Flag	Coverage Δ
angular	100.0% <ø> (ø)
universal	100.0% <100.0%> (ø)

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commit: 7a919ff