[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)

src/traces/sankey/render.js の 76-78 行付近にある警告から始め、アップグレードされた @plotly/d3-sankey v0.12.3 の padding API と、レイアウト後のノード位置を比較します。実効 padding をどのように検出すべきか、または警告を削除すべきかを解決し、診断動作がクランプされたレイアウトと一致することを検証します。