Put each repository tab's filters and search on one row

Put each repository tab's filters and search on one row

The filter controls had grown into two rows on the pages that also had state
chips: the chips sat above, the search and dropdowns below. Where the search sat
also depended on the page, so moving from issues to changes to code changed the
order of the same controls.

Every filter row now reads left to right: chips and labelled dropdowns on the
left, the search group on the right, with the clear action in the same right
group on pages that have no text search. The chips moved inside the form on
issues, changes and activity so a search keeps the chosen state or kind, and an
htmx swap replaces the whole row with the values the server rendered.

The row is one `.filters` element with a `.filters-search` group, so code search
and the global search page use the same shape rather than a second one. On a
phone the row stacks and the search stays on one line with its button.