fix: Rename both tags when one is being edited

[Nishthajain7]

Issue:

Fixes #3873

Demo:

Screencast.from.2026-02-22.21-24-21.webm

Changes:

I used syntaxTree from codemirror to traverse through an html tree and find the corresponding closing tag of the opening tag that is being edited.

I have verified that this pull request:

• has no linting errors (npm run lint)
• has no test errors (npm run test)
• has no typecheck errors (npm run typecheck)
• is from a uniquely-named feature branch and is up to date with the develop branch.
• is descriptively named and links to an issue number, i.e. Fixes #123
• meets the standards outlined in the accessibility guidelines

[Jatin24062005]

The overall approach looks solid and CM6-native
Using the syntax tree to sync opening and closing tags (with an annotation guard to avoid recursion) seems like a good fit for this regression.
One small process note: for changes of this size, it’s usually helpful to comment on the issue and wait for maintainer confirmation or assignment before opening a PR.