[BUG]: Sankey warning breaks in @plotly/d3-sankey v0.12.3

Description

The upgrade to @plotly/d3-sankey v0.12.3 (in #7830) will break the warning here:

if (sankey.nodePadding() < nodePad) {
    Lib.warn('node.pad was reduced to ', sankey.nodePadding(), ' to fit within the figure.');
}

In @plotly/d3-sankey@0.7.x, calling sankey.nodePadding() after running the layout returned the effective (post-clamp) padding value. In 0.12.3 the getter returns the user-configured value instead, because upstream split the internal state into separate dy (configured) and py (effective) variables.

After the upgrade, sankey.nodePadding() always equals nodePad, so the comparison is never true and the warning never fires. The layout itself still clamps correctly - only the diagnostic is affected.

Notes

Options to address the issue:

• Remove the warning entirely
• Derive the effective padding from the laid-out node positions (e.g. measure the gap between consecutive nodes in the densest column)

Start in src/traces/sankey/render.js at the warning around lines 76-78, then compare the upgraded @plotly/d3-sankey v0.12.3 padding API with the laid-out node positions. Resolve how the effective padding should be detected or whether the warning should be removed, and verify that the diagnostic behavior matches the clamped layout.