Modern UI: sash resize target sits inside panel gap, not on the visible edge

[mrleemurray]

Feedback

I want this gap to be smaller. it's also a break of my muscle memory that in order to resize the view, I have to grab inside of gap instead of on the line

Source: #workbench-refresh-feedback — 2026-06-26
Screenshot: https://slack-files.com/T0HLXG4VA-F0BEAHANC8Y-65a44a2763

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Context

With floating panels and the increased outer gutter (FLOATING_PANEL_MARGIN), the sash hover/drag area sits visually inside the gap between panels rather than aligned with the visible panel edge. Users expect to grab the visible border line to resize — having to target the interior of a wide gap breaks established muscle memory and makes resizing feel imprecise and hard to discover.

Acceptance Criteria

• The sash hit target aligns with the visible panel edge rather than the center of the gap between panels
• Resizing panels by clicking on their visible border feels natural and matches user expectation
• The gap width and sash offset are tuned so the grab zone does not feel detached from the panel boundary

[DonJayamanne]

Ran into this issue immediately, and took me a while to figure out that there was a small blndspot
If the cursor comes in from the left it works perfectly, however if the cursor comes in from the right of the gap (separators), you can see that clicking has no effect and there's no drag indicator either.
I.e. when moving cursor from left, i need to move to the middle of the gap