nav bar: can hide while navigating, or until the screen is tapped

Set in car Settings. Off "Always show", the bar floats over the map, so
hiding it never resizes the map app's surface; the app is told the bar
covers the bottom while it shows. The arrival card no longer counts as
covering the map, so Waze's speedometer sits level with it.

gearslip/src/main/java/app/seb3thehacker/gearslip/car/CarSettingsScreen.kt

@@ -51,6 +51,7 @@ fun CarSettingsScreen() {
     val open by CarSettings.openOnConnect.collectAsState()
     val night by CarSettings.nightMode.collectAsState()
     val units by CarSettings.units.collectAsState()
+    val navBar by CarSettings.navBarMode.collectAsState()
     val whatsNew by CarSettings.whatsNewAfterUpdates.collectAsState()
     val pipeAudio by CarSettings.pipeAudio.collectAsState()
     val speakDirections by CarSettings.speakDirections.collectAsState()
@@ -115,6 +116,16 @@ fun CarSettingsScreen() {
             units,
         ) { CarSettings.setUnits(it) }
 
+        ChoiceRow(
+            "Nav bar",
+            listOf(
+                NavBarMode.SHOW to "Always show",
+                NavBarMode.HIDE_NAVIGATING to "Hide while navigating",
+                NavBarMode.HIDE to "Hide until tapped",
+            ),
+            navBar,
+        ) { CarSettings.setNavBarMode(it) }
+
         ChoiceRow(
             "Player in the nav bar",
             listOf(false to "Skip buttons", true to "Song title"),