Searching within a tag page will search the contents of that tag by default.

## Is your feature request related to a problem? yes

## Describe the solution you'd like

Searching within a tag page will search the contents of that tag by default.Many users do not know how to use advanced search when they first start using it, and it is difficult for them to search for content within a certain tag.

## Describe alternatives you've considered

Or add a separate search box in the tag page to search the content under the tag.

Start at the tag page and its search entry point, then trace how searches are currently scoped. Compare the requested default tag filtering with the alternative separate search box, and define done as a clear, tested search behavior for content under the selected tag.

Written by the indexing model from the issue text.