[Bug]: Large diff panel jumps and drifts while scrolling

[Khrisseh1995]

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/web

Steps to reproduce

1. Open a Working tree diff containing several files with substantially different lengths.
2. Scroll continuously from the first file to the final file.
3. Compare the scroll position with the visible file and inspect the virtualized container's computed and inline top.
4. Collapse every file, then compare the layout with the override removed globally.

Expected behavior

• The rendered file and line remain aligned with the scrollbar.
• Scrolling crosses file boundaries smoothly.
• When every file is collapsed, the first file header remains aligned directly below the toolbar.

Actual behavior

• The virtualizer's inline top changes, but its computed top remains 0px.
• Content progressively drifts behind the scroll position and file transitions become visibly jumpy.
• Removing the override globally fixes expanded scrolling but brings back an approximately 41 px spacer above the all-collapsed file list.

Impact

Minor bug or occasional failure

Version or commit

v0.0.29-nightly.20260725.898 (regression: 38cfc25)

Environment

Arch Linux; T3 Code Nightly v0.0.29-nightly.20260725.898; Chrome 149

Screenshots, recordings, or supporting files

issue-reproduction-nightly.mp4

[t3-code]

fixed by #4724, merged in 3c50a64. it restores virtualized diff positioning and corrects collapsed spacing metrics, resolving the reported scrolling jump/drift. closing as completed.