Nested `U+0022` are considered to be erroneous.

#### How To Reproduce It

Into [`github.com/gildas-lormeau/SingleFile/issues/1917#_r_g7_`](https://github.com/gildas-lormeau/SingleFile/issues/1917#_r_g7_:~:text=Roke%20Julian%20Lockhart-,Add%20a%20comment,-new%20Comment), I entered:

~~~markdown
> It would also help to know whether this happens with all pages or only some of them, and whether it still happens when "open the "Save as" dialog to confirm the file name" is disabled in the options.
~~~

#### The Expected Behaviour

It should parse the quotation marks, from the outside, inward.

#### Screenshots

#### My Environment

I am utilising [`addons.mozilla.org/firefox/downloads/file/4957307/private_grammar_checker_harper-2.8.0.xpi`](https://addons.mozilla.org/firefox/downloads/file/4957307/private_grammar_checker_harper-2.8.0.xpi), on [`packages.mozilla.org/rpm/firefox/Packages/3fe459398e441fa384477eebaafb235b61cb7521e5d44711a64978e82f25dbf9-firefox-nightly-157.0a1-20260827182558`](https://packages.mozilla.org/rpm/firefox/Packages/3fe459398e441fa384477eebaafb235b61cb7521e5d44711a64978e82f25dbf9-firefox-nightly-157.0a1-20260827182558.x86_64.rpm).

#### Additional Context

This may affect [`issues/4131`](https://github.com/Automattic/harper/issues/4131#issue-5194688181).

No source file or test is named. Start by reproducing the exact blockquote in the Firefox extension, then trace how nested U+0022 quotation marks are parsed and diagnosed. Done means the quoted sentence, including the nested "Save as" text, is accepted without an erroneous diagnostic.

Written by the indexing model from the issue text.