Documents: \( pairs stay in one paragraph and off addresses; formulas place at wraps

- Pairs pair inside one paragraph, heading or cell; links' addresses,
  images, code and <code>/<kbd> text stay literal.
- Adjacent formulas stay two; a parting space is dropped after parsing.
- Stray and escaped dollars, in or out of a formula, stay dollars.
- A formula's node spans its delimiters; its value is the written TeX.
- A formula wrapped whole draws at its own line's start.
- A failed inline formula shows its reason after the TeX.

Co-Authored-By: Claude <noreply@anthropic.com>

src/typography/math.rs

@@ -193,7 +193,7 @@ fn framed(svg: &str, width: f32, height: f32) -> Result<(String, Size<Pixels>),
     Ok((wrapped(svg, [left, top, w, h])?, size(px(w), px(h))))
 }
 
-/// `svg`'s drawing under a root viewing `[left, top, w, h]` in px.
+/// `svg` drawn in a px root viewing `[left, top, w, h]`.
 fn wrapped(svg: &str, [left, top, w, h]: [f32; 4]) -> Result<String, MathError> {
     let open = svg
         .find('>')