upstream was right about the weird padding

see "Navigation bar target size and margins" in
https://m3.material.io/components/navigation-bar/specs

mastodon/src/main/res/layout/tab_bar.xml

@@ -12,7 +12,8 @@
 	<org.joinmastodon.android.ui.views.TabBar
 		android:id="@+id/tabbar"
 		android:layout_width="match_parent"
-		android:layout_height="56dp">
+		android:layout_height="56dp"
+		android:paddingHorizontal="8dp">
 
 		<FrameLayout
 			android:id="@+id/tab_home"