`cite(form: "prose")` does not work well with superscript citation styles

[YDX-2147483647]

This issue was originally reported by 液氦杯面🍜 in the Chinese community.

A CSL may specify vertical-align="sup" to render citations in superscripts. gb-7714-2015-numeric is an example.

For such styles, cite(form: "prose") puts the citation number in a superscript, but puts the affixes on the baseline. That looks ugly.

I suggest we include the affixes in the superscript.

Minimal example

test.csl

<?xml version="1.0" encoding="utf-8"?>
<style xmlns="http://purl.org/net/xbiblio/csl" class="in-text" version="1.0">
  <info>
    <title/>
    <id/>
    <category citation-format="numeric"/>
  </info>
  <citation>
    <layout vertical-align="sup" prefix="[" suffix="]">
      <text variable="citation-number"/>
    </layout>
  </citation>
  <bibliography >
    <layout>
      <names variable="author"/>
    </layout>
  </bibliography>
</style>

- Normal form @a
- Prose form: #cite(<a>, form: "prose")

#bibliography(
  bytes("@article{a, author = {Author}}"),
  style: "test.csl",
)

Typst v0.15.1 paged output:

Typst v0.15.1 HTML output (This eliminates the possibility of font issues):

<ul>
  <li>Normal form<sup role="doc-biblioref">[</sup><a href="#loc-1" role="doc-biblioref"><sup>1</sup></a><sup role="doc-biblioref">]</sup></li>
  <li>Prose form: <a href="#loc-1" role="doc-biblioref">Author [<sup>1</sup>]</a></li>
</ul>

Expected output:

Relevant code

hayagriva/src/csl/mod.rs

Lines 1847 to 1854 in 9781848

	// Print the label.
	if let Some(prefix) = self.csl.citation.layout.prefix.as_ref() {
	ctx.push_str(prefix);
	}
	do_regular(&mut ctx);
	if let Some(suffix) = self.csl.citation.layout.suffix.as_ref() {
	ctx.push_str(suffix);
	}