fix: don't escape [ bracket in linktext

[Soxasora]

Description

Fixes #2879

gfm-footnote toMarkdown extension marks [ as unsafe in phrasing to protect from unwanted footnotes or nested links, but footnotes or nested links can't start anyway inside of linktext.
This PR unescapes [ square brackets inside of linktext (text node inside of a link node).

Screenshots

unescape.mov

Additional Context

One of the goals of future stages is to implement a better method for customizing escaping.

Checklist

Are your changes backward compatible? Please answer below:

For example, a change is not backward compatible if you removed a GraphQL field or dropped a database column.
Yes
On a scale of 1-10 how well and how have you QA'd this change and any features it might affect? Please answer below:
7

For frontend changes: Tested on mobile, light and dark mode? Please answer below:
n/a

Did you introduce any new environment variables? If so, call them out explicitly here:
n/a

Did you use AI for this? If so, how much did it assist you?
review, tests

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Note

Low Risk
Low risk: narrow change to Markdown serialization that only alters escaping behavior inside link text; main risk is minor formatting regressions in edge-case link rendering.

Overview
Fixes Lexical-to-Markdown export so link text no longer keeps escaped \[ characters introduced by the gfm-footnote phrasing safety rules. The link toMarkdown handler now unescapes [ within link text while still emitting standard [text](url "title") syntax.

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Unescaping [ in link text breaks outer link parsing

Medium Severity

The .replace(/\\\[/g, '[') regex unescapes all \[ in link text, but an unescaped [ inside link text can combine with the outer link's ](url) to form an unintended inner link, breaking the outer link entirely. For example, a link with text click [here and URL url would serialize to [click [here](url), which CommonMark parses as literal [click plus a link here→url — the intended outer link is destroyed. The escaping that state.safe() applies to [ is necessary to prevent inner bracket sequences from taking precedence over the outer link structure per the CommonMark spec.

 

[Soxasora]

I see, and it makes sense. Maybe escaped brackets don't cause issues, I'll think about this.