fix(ui): a caption never opens under a finger

On an iPad a tap's synthetic mouseenter opened the Tooltip; WebKit then took the
tap as a hover and swallowed its click, so every rail button needed two taps,
and with no mouseleave from a finger the caption stayed up. Tooltip now opens
for a mouse and a key's focus only (owner: no captions on touch).

frontend/src/components/ui/Tooltip.tsx

@@ -37,6 +37,8 @@ export default function Tooltip({
     // Show/hide on contact by default (as the pre-platform tooltip did); `openDelay` adds a
     // rest-before-show for labels that shouldn't flash on a fast sweep across an icon row.
     hoverDelay: { open: openDelay, close: 0 },
+    // A caption is for a mouse (and a key's focus). Opened by a tap it cost touch the tap itself.
+    mouseHoverOnly: true,
   });
   const { setReference } = pop.refs;