`@html.svg` and `@html.math` create elements without SVG/MathML namespaces

[yorkin-bot]

Summary

The convenience constructors @html.svg and @html.math both delegate to the generic HTML node constructor. That produces VNodes with no namespace, so the runtime calls document.createElement instead of document.createElementNS.

As a result, these constructors do not create real SVG or MathML elements in an HTML document.

Evidence

• Generic node creates a VNode without a namespace
• @html.svg and @html.math both call node
• The runtime selects create_element when namespace is absent
• The dedicated SVG package correctly defaults to the SVG namespace

A white-box test inspecting the VNode created by @html.svg observed:

expected: Some(http://www.w3.org/2000/svg)
actual:   None

The same source path gives @html.math a None namespace.

Expected behavior

• @html.svg should use http://www.w3.org/2000/svg.
• @html.math should use http://www.w3.org/1998/Math/MathML.

The resulting browser elements should have the correct namespaceURI and native element type.

Additional MathML blocker

After adding the MathML namespace, style handling also needs attention. The runtime style branch accepts only HTMLElement or SVGElement and otherwise panics:

• style application casts only to HTML or SVG elements

A namespaced MathML element is neither, so fixing only the namespace can expose a second failure even when the style list is empty.

Suggested tests

• Assert both constructors retain the expected namespace in the VNode.
• In a browser test, assert each element's namespaceURI.
• Verify SVG rendering and MathML creation/update, including the empty-style path.