fix: allow clicking into hover tooltips to select and copy content

[ndoschek]

What it does

Resolves GH-15986

• Check if mousedown target is inside the hover host before canceling, so clicks within the tooltip no longer dismiss it
• Add user-select: text to the hover CSS to ensure text is selectable

How to test

1. Hover over an element that shows a static tooltip (e.g. title of any sidebar view like Explorer)
2. Click and drag or doubleclick to select text inside the tooltip, verify text selection works and content can be copied
3. Click outside the tooltip and verify it dismisses as expected
4. Hover over an element that shows an interactive tooltip (e.g. the language status bar item { })
5. Click an action in the hover tooltip, verify it stays open and does not dismiss

Follow-ups

Breaking changes

• This PR introduces breaking changes and requires careful review. If yes, the breaking changes section in the changelog has been updated.

Attribution

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines
• User-facing text is internationalized using the nls service (for details, please see the Internationalization/Localization section in the Coding Guidelines)

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

[sgraband]

Thanks LGTM 👍