What kind of change does this PR introduce?

• Bugfix
• Feature
• Documentation
• Code style update
• Refactor
• Build-related changes
• Other, please describe:

Does this PR introduce a breaking change?

• Yes
• No

The PR fulfills these requirements:

• It's submitted to the dev branch (or v[X] branch)
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix: #xxx[,#xxx], where "xxx" is the issue number)
• It's been tested on a Cordova (iOS, Android) app
• It's been tested on an Electron app
• Any necessary documentation has been added or updated in the docs or explained in the PR's description.

If adding a new feature, the PR's description includes:

• A convincing reason for adding this feature (to avoid wasting your time, it's best to start a new feature discussion first and wait for approval before working on it)

Other information:

When selecting text with mixed formatting (e.g., **bold** plain) and applying a hyperlink via the Link toolbar button, the hyperlink was not being applied to the full selection.

Root Cause:

document.execCommand('createLink') mutates the DOM by splitting a mixed-format selection into separate <a> elements per formatting context:

<!-- Before createLink -->
<strong>34</strong> text

<!-- After createLink — browser creates two separate anchors -->
<a href="https://"><strong>34</strong></a><a href="https://"> text</a>

The selection range was saved after this mutation, so getRangeAt(0) only captured the first <a> element's range. When the user confirmed the URL, restore() reselected only that partial content, and the final createLink only updated one anchor's href.

Fix:

Move this.save(selection.getRangeAt(0)) to before document.execCommand('createLink', ...) in ui/src/components/editor/editor-caret.js, so the full original selection is preserved before the DOM is mutated.

Since createLink only re-parents existing text nodes (it doesn't create new ones), the saved range node references remain valid after the mutation. restore() then correctly reselects the full original content, and the final createLink call updates all anchor href values.

fixes #18233