fix(ui): Hide the focus outline around dropdown popups

The global :focus-visible rule loads after the module CSS and has the same
specificity, so it overrode `outline: none` on the focused listbox wrapper
and drew a square blue frame inside the Select popup.

Claude-Session: https://claude.ai/code/session_01B65qLEKnkeYTGdbwhLpjCu

src/ui/Select.module.css

@@ -57,10 +57,13 @@
   overflow: hidden;
 }
 .popupInner {
-  outline: none;
   display: flex;
   flex-direction: column;
 }
+/* Focus only carries keystrokes; the active row is the indicator. */
+.popupInner:focus-visible {
+  outline: none;
+}
 .list {
   max-height: 320px;
 }