Scroll a long section nav instead of wrapping it onto a grid

Five or more sections wrapped onto a 3- or 4-column grid, which left the tab
bar's divider under the last row only and stranded every upper row's active
indicator against nothing. From five they are now what M3 prescribes and its
accessibility page defends: a scrollable tab bar, each tab as wide as its label,
offset 52dp. Four or fewer still share the row. The 20px icons take the 20 cut.
Plan: docs/plans/material-3-alignment.md, step 21 (navigation N-16).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Qwx5USif3wFFmxtHg5U1g9

resources/css/components/tabs.css

@@ -65,6 +65,7 @@
         transition: color var(--md-sys-motion-effects-fast-duration) var(--md-sys-motion-effects-fast);
     }
 
+    [data-tabs-bar][data-scrollable] > li,
     [data-tabs-bar][data-scrollable] [data-tab] {
         flex: none;
     }