feat(md): add md util for truncating around <macro_em> search tags for soup

[sedson]

Summary

Screenshots, GIFs, and Videos

[linear]

M-5454 Static Markdown singleLine not working -> losing info during search

[gbirman]

I pulled locally and a lot of these results still aren't working well imo. This is the content of the first one btw where it only grabbed the date:

" 29, 2025
<macro_em>Hey</macro_em> — quick reminder.
If you want to start 2026 with a"

Lmk if you need more examples to play around with.

also we have packages/core/util/searchHighlight.ts already I'd move the utils into there if possible

EDIT: saw that we didn't have a truncate search match markdown util on the email content match, lemme try that

[gbirman]

ok looks email looks better with that util. BTW I'm noticing ## prevents markdown from highlighting the "hey" string from the image above, could you look into that:
"## <macro_em>Hey</macro_em> gbirman1998, let's verify your email address\nVerifying your email enables you to collaborate"

[gbirman]

Ok so here's the requested changes summary:

• leave props.data.content as is in entitywitheverything and instead update packages/macro-entity/src/queries/search.ts getSearchData function to have:

content: YOUR_UTIL_FN(mergeAdjacentMacroEmTags(content)),

• remove LexicalMarkdown/searchUtils and move the utils into packages/core/util/searchHighlight.ts

• fix the ## bug I mentioned