[Component] [tabs] Default mode bottom border does not cover add-icon slot area

Bug Type: Component

Environment

• Vue Version: 3.5.42
• Element Plus Version: 2.14.5
• Browser / OS: Chrome 152.0.7977.83/Windows 10
• Build Tool: Vite

Reproduction

Related Component

• el-tabs

Reproduction Link

Element Plus Playground

Steps to reproduce

1. Open the playground link above.
2. Compare the two Tabs (default type vs type="card").

What is Expected?

In default mode, the bottom border should also cover the add-icon slot area (same as card / border-card mode).

What is actually happening?

In default mode the bottom border stops before the add-icon slot, while in card mode it covers the whole header.

Additional comments