Site-wide tooltip & dropdown visibility fix + Cron tool UX polish

While reviewing the Cron expression tool we found that hover tooltips had stopped working on the live site: moving the cursor over the preset chips, the favorite button, or other elements that should show a small hint bubble produced nothing you could actually read.

Why popups were invisible

The tooltip content was actually being inserted into the page when you hovered — it just stayed fully transparent. A CSS minification quirk reordered the stylesheet so that the "hidden" state of Semi UI popups always beat the "shown" state, no matter what. The same bug had silently hit dropdown menus too: the extract button's dropdown was technically opening all along, you just couldn't see it.

Tooltips and dropdown menus now display correctly everywhere on the site, including the favorite star hint, Cron preset previews, LaTeX symbol hints, and workspace button hints.

Cron tool interaction improvements

• Preset chips: the hover preview now waits briefly before appearing, so sweeping the cursor across the preset row no longer produces rapid flashing — stop on a chip to see its expression.
• Field reference cards: the five cards (minute / hour / day / month / weekday) used to always show *. They now reflect the actual field values of the current expression — for 0 9 * * 1-5 they show 0, 9, *, *, 1-5, and non-wildcard fields are highlighted with the theme color.