[Bug]: dragging resize handles between panels is buggy using touch input #33056

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. start a new thread and open the bottom and right side panel
2. on a Googlebook or tablet, use the touch screen and attempt to drag the drag grab handles to resize the panels

Expected behavior

the handle of the panel should move and be locked to the finger as soon as it is depressed, and continue to move until the finger is released

Actual behavior

observe how the panels only seem to move when the finger overlaps a very small segment of the handle otherwise it will jitter or not move at all.
it is expected to be able to use touch alongside keyboard and trackpad for an on the to experience.
it is meaningfully impossible to resize the handles in this state, making it hard to do adequate reviews on files generated by agents.

Impact

Major degradation or frequent failure

Version or commit

main @ 322f654

Environment

Android 17, Googlebook OS 17, Chrome 157

Logs or stack traces

Screenshots, recordings, or supporting files

No response

Workaround

No response