Give the tab rail its own glass bar and reserve space for it

The three tab buttons now share one frosted glass pill instead of each
floating separately, and BrowseView/RoomView reserve TAB_RAIL_CLEARANCE
of right-side padding so a full-width row or grid never renders under
it - verified against the real library, where dense rows (e.g. Conni's
82 audiobooks) previously butted right up against the rail.

Also gitignore the real (non-.example) tippen-curriculum.yml and
tippen-progress.json, matching config.yml's own privacy treatment,
since the curriculum now contains real reward paths into a personal
library.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/src/lib/theme.ts

@@ -75,6 +75,12 @@ export const GROUP_LABEL: Record<Group, string> = {
   podcasts: "Podcasts",
 };
 
+/** How much horizontal space the tab rail's own glass bar claims on the right edge
+ * (its `right` inset plus its rendered width) - scrollable content reserves this much
+ * padding on that side so a full row/grid never renders underneath it. Keep in sync
+ * with the geometry in `TabRail.tsx`. */
+export const TAB_RAIL_CLEARANCE = 88;
+
 /** Icon/label for the vertical tab rail - one entry per `UiState["page"]`. The
  * smarthome tab only renders when Home Assistant is configured (see `App.tsx`); the
  * other two always show. */