[ feature ] Support the new Topbar (2nd-row)

[JorgeR81]

The latest ComfyUI front end allows you to place workflows in a 2nd row.

• Support 2nd row location for workflow tabs Comfy-Org/ComfyUI_frontend#2193

This gives more space for buttons in the Topbar.

It would be nice if the Controllers snapped this to this 2nd row, when it's enabled.
Currently, they will just cover the 2nd row, so we need to manually adjust the position.

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By the way, even if we add lots of workflow tabs, we will never need more rows, thanks to this other feature:

• Horizontal scroll workflow tabs on overflow Comfy-Org/ComfyUI_frontend#2188

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But we may also need some aesthetic adjustments, because the 2nd row it's only filled where there are workflow tabs.

It would look better if the whole 2nd row was filled, if any Controller window was stacked to it.

original:

mockup:

We lose a bit of canvas space, but it will work in a more consistent way.
Besides, this will make the canvas a perfect rectangle again, and some users prefer that look.