fix: withdraw the quote attribution, a captioned quote is a figure again

[dereuromark]

What

A caption on a block quote is a figure caption again. block_quote.attribution is gone, figure.target admits a block_quote, and the spec submodule moves onto the withdrawal.

Implements markup-carve/carve#1213, which withdraws PART 9 section 4a and PART 11 section 10d.

Why the clause fell

The HTML Standard's blockquote section:

Attribution for the quotation, if any, must be placed outside the blockquote element.

and its recommended pattern, given as the way "to clearly relate a quote to its attribution (which is not part of the quote and therefore doesn't belong inside the blockquote itself)":

<figure>
 <blockquote>
  <p>The truth may be puzzling. ...</p>
 </blockquote>
 <figcaption>Carl Sagan, in "<cite>Wonder and Skepticism</cite>", ...</figcaption>
</figure>

Section 4a put the attribution inside the quote, in a <footer>, and asserted in its own text that both spellings were valid HTML.

Its model argument fails too. figure is already the generic captioned wrapper in this engine: a captioned code block is a figure whose target is the code block. What a captioned thing is called and counted as comes from the caption's own label, not from the host's node type, so a quote was never a special host.

Nothing shipped. 0.1.2 predates #946, so this removes code no release carried, and the CHANGELOG loses those entries rather than gaining a reversal.

What comes back

> To be
^ Hamlet

<figure>
  <blockquote><p>To be</p></blockquote>
  <figcaption>Hamlet</figcaption>
</figure>

The caption numbers like any other. Measured on this branch:

{#ep}
> To be
^ Figure #: Hamlet

![x](/i.png)
^ Figure #: An image

See </#ep>.

<figure id="ep">
  <blockquote><p>To be</p></blockquote>
  <figcaption>Figure 1: Hamlet</figcaption>
</figure>
<figure>
  <img src="/i.png" alt="x">
  <figcaption>Figure 2: An image</figcaption>
</figure>
<p>See <a href="#ep">Figure 1</a>.</p>

• BlockQuote.attribution is gone from the node, the AST JSON codec and every walk, extension and renderer that carried it, and FigureTarget::BlockQuote is back. src/wire_fields.rs is regenerated from the moved spec submodule rather than hand-edited.
• A <footer> inside a quote is ordinary quoted content again on the import path.
• The Markdown, plain-text and terminal writers lose the attribution-specific handling section 10d added (the <footer> element, the quote bar carried onto the attribution line, the removed blank line) and render a quote's caption the way they render any other figure caption.

What stays

PART 11 section 10e landed in the same commits and is untouched: a table caption still survives the Markdown target, and a code fence's title and grouping label still survive plain text and the terminal. Measured on this branch:

| H |
| --- |
| a |

Table caption

Multi-block captioned quotes also keep working. The pre-4a oracle refused them; that regression does not come back.

Cross-engine

Measured against carve-js on its matching branch: the HTML, Markdown, plain-text and terminal output for a captioned quote is byte-identical in both engines, and a numbered caption resolves to the same "Figure 1" cross-reference.

Downstream

markup-carve/carve-js and markup-carve/carve-php get the same revert. markup-carve/carve-grammars#219 tracks the tiptap projection.