Line breaking in a code span can break the block structure

In CommonMark rendering, line breaking in a code span can break the block structure. Here are just a few examples:

$ printf '`xx --- xx`' | cmark -t commonmark --width 3 | cmark -t html
<h2>`xx</h2>
<p>xx`</p>
$ printf '`xx ``` xx`' | cmark -t commonmark --width 3 | cmark -t html
<p>`xx</p>
<pre><code>xx`
</code></pre>
$ printf '`xx + x xx`' | cmark -t commonmark --width 3 | cmark -t html
<p>`xx</p>
<ul>
<li>x
xx`</li>
</ul>

In case anyone wants to discuss, here is my attempt to specify how I think CommonMark rendering should work:

Line breaking is only implemented inside a paragraph, not inside a heading or an HTML block.

Except inside raw HTML (which I've not thought about), any group of consecutive whitespace characters will turn into a single space or a newline followed by the current line prefix.

Break each line at the last breakable space that doesn't make the line too long. So a line will be wider than the specified width only if it contains no breakable spaces.

In code spans a space is breakable if and only if the following group of non-space characters does not match any of the following Perl regular expressions:

/^[#*-=_]+$/      thematic break, heading
/^(```|~~~)/      fenced code block
/^[<>]/           HTML block, block quote
/^[*+-]$/         list item
/^[0-9]+[).]$/    list item

In textual content all spaces are breakable. A backslash is inserted for the following groups of characters:

/[*<[\\_`]/       escape, code, emphasis, links, images, raw HTML
/[&][#A-Za-z]/    entity or numeric character reference
/^[#*-=_]+$/      thematic break, heading
/^(```|~~~)/      fenced code block
/^[<>]/           HTML block, block quote
/^[*+-]$/         list item
/^[0-9]+[).]$/    list item

In these expressions, ^ means the start of a line (perhaps following a line prefix) and $ means space or the end of the line.

The backslash is inserted in front of each group, except in the last case, where it is inserted in front of the parenthesis or dot.

I've almost certainly forgotten something in there.

Reproduce the reported cases with the cmark commands in the issue, especially the code-span inputs rendered with --width 3. Read the proposed line-breaking rules and compare them with CommonMark parsing and rendering behavior. Done means line breaking inside code spans no longer changes headings, paragraphs, fenced code blocks, or list structure.