[priard]

Problem

In Both sides, the gap between the left group and the right group shrinks as magnification grows the icons. When the resting gap is small (a row that nearly fills the width), the growth uses the gap up. Its width then reaches 0, and the right group jumps left by one row spacing before it carries on. This was the one minor left open from the #49 review.

Cause

A Row does not lay out a child with zero width, and it drops the spacing after that child too. So the right group goes from gapX + gap + spacing to gapX in one frame.

Fix

DockLayout.spreadGap bottoms out at one device pixel (one logical pixel without a scale) instead of 0. The Row keeps the gap item and its spacing, so the right group keeps moving the way it was. At rest nothing changes, except in a gap already narrower than one pixel.

Not in this PR

Once the growth is larger than the whole resting gap, the right group still runs past the card's right edge. Panel with Center or Right does the same near full width, where rowOffset stops at 0. Keeping it on the card would mean moving the row left during magnification. That would shift pointerX against the resting centres, and the wave would start chasing itself. I left it as is; it needs a row that nearly fills the screen.

Testing

• tests/unit/layout.test.mjs: the floor in logical and device pixels, plus a sweep that pushes the left group through the moment the gap runs out. On the old code the sweep catches the 6 px jump; with the fix it passes.
• CI-equivalent checks pass locally, including structure-check.py.
• tests/live/layout.sh passes and the smoke test is clean.
• Not checked by eye: getting a small resting gap needs a row that nearly fills 5120 px.

[thepathless]

🎉 Thank you so much for this contribution, @priard! Really appreciate the care you put into it. ✨ Verified on experimental — static gates, unit suites (239 node + 116 python) and the full live dock battery all green, including the marks-centering suite — and merged. Your work is credited in the changelog. 🙏🚀