fix(ui): Tabs is an ARIA tab list with roving focus and a wired panel

The rail was a row of aria-pressed toggles: every tab a Tab stop, no arrows,
nothing tying a tab to its content. tablist/tab/aria-selected, one Tab stop,
arrows on either axis, Home/End, and useTabPanel for aria-controls/labelledby.

frontend/src/lib/theme.contract.test.ts

@@ -72,7 +72,7 @@ it("the state layers stand down on a disabled, busy or pressed control", () => {
     for (const [, state, sel] of states) expect(sel, `${name} :${state}`).toMatch(guard);
   }
   expect(css.slice(css.indexOf("@utility state-layer {"))).toMatch(
-    /&:hover:not\([^)]*\[aria-pressed="true"\]\)/,
+    /&:hover:not\([^)]*\[aria-pressed="true"\][^)]*\)/,
   );
 });