Fix search icon button in top bar for touch devices

Ensure height of search icon button doesn't exceed height of top bar.
This is necessary because the containing form has a white background.
Other icon buttons in the top bar also exceed the height of the bar on
touch devices, but this isn't evident because they have transparent
backgrounds.

Fixes https://github.com/hypothesis/client/issues/5308

src/sidebar/components/SearchInput.tsx

@@ -195,6 +195,16 @@ export default function SearchInput({
             onClick={() => input.current?.focus()}
             size="xs"
             title="Search annotations"
+            // The containing form has a white background. The top bar is only
+            // 40px high. If we allow standard touch-minimum height here (44px),
+            // the visible white background exceeds the height of the top bar in
+            // touch contexts. Disable touch sizing, then add back the width
+            // rule to keep horizontal spacing consistent.
+            // FIXME:
+            // Button/IconButton are due a pass for responsive styling and
+            // appropriate styling API controls (@hypothesis/frontend-shared)
+            disableTouchSizing
+            classes="touch:min-w-touch-minimum"
           />
         </div>
       )}