A cleaner, more familiar tab strip and tab groups

The tabs got a quieter, more familiar look. Instead of every tab wearing its own outline, tabs now float as soft rounded chips and only the one you are on stands out as a raised white tab, so the strip reads calm at a glance and your current tab is obvious. Tab groups were rebuilt to match: a group is now one soft band of colour holding a rounded name pill and its tabs, so a group reads as a single thing rather than a row of boxed-in tabs. Groups line up exactly with the rest of your tabs, the full group name always shows, and clicking the name tucks the whole group down to a small coloured pill with a count, then back again.