A [*] checkbox the reader refuses loses the checklist reading and moves a bold run

What happens

* [*] a
 +
para
  *b
  c* d

Both programs render <p>&#10003; a <br> para <strong>b c</strong> d</p>. The formatter writes * [*]\na\n +\npara *b c* d\n, which both programs render <p>[<strong>] a <br> para *b c</strong> d</p>: the checklist reading is gone and the bold run has moved.

A second face of the same cluster: * [*] a\n +\n// c\n *b\n c* d\n formats to * [*] a +\n// c\n*b c* d\n; the item stays a checklist, but the literal + becomes a <br> (#304's common-indent mechanism reappearing because the refused prefix leaves four extra columns inside the text).

Mechanism

stripCheckboxPrefix (src/parse/build/list.ts) refuses the prefix when the leading text node does not carry all four characters, which happens to [*] whenever the item's text holds a later * for the checked marker's own * to pair with. The comment at the refusal calls this "a divergence in the one direction that cannot corrupt text"; these documents are counterexamples under both programs.

How it was found

The #314 population (a checklist first-line dimension of the reflow-line sweep, 16,723 added documents): one cluster of three documents, indented-two-line/fidelity, tagged with this issue.

Related

#314, #304, #316, #140.

Start in src/parse/build/list.ts at stripCheckboxPrefix and reproduce the three documents in the #314 population, especially indented-two-line/fidelity. Compare the formatter output with the two reference renderings, then add coverage showing that the checklist reading, bold span, and literal + remain unchanged.