App 2.27.1: accent colour only for styles drawn in it

Settings → Display now has the Overview style first with the accent
colour beside it; for styles with their own palette the accent field is
greyed out with a note. Styles are an enum, OverviewStyle, with
usesAccent (unit-tested). Emulator only.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LhzAVaUyqcw5PkGjz4mWW6

app/src/test/java/com/evsuite/abrp/OverviewStyleTest.java

@@ -0,0 +1,35 @@
+package com.evsuite.abrp;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+/** The Overview styles — pure JVM. */
+public class OverviewStyleTest {
+
+    @Test
+    public void storedValuesRoundTrip() {
+        for (OverviewStyle style : OverviewStyle.values()) {
+            assertEquals(style, OverviewStyle.fromPref(style.name()));
+        }
+    }
+
+    @Test
+    public void oldAndUnknownValues() {
+        assertEquals(OverviewStyle.GAUGES, OverviewStyle.fromPref("DASHBOARD"));
+        assertEquals(OverviewStyle.TILES, OverviewStyle.fromPref(null));
+        assertEquals(OverviewStyle.TILES, OverviewStyle.fromPref("NOPE"));
+    }
+
+    @Test
+    public void onlyStylesDrawnInTheAccentOfferIt() {
+        assertTrue(OverviewStyle.TILES.usesAccent);
+        assertTrue(OverviewStyle.RETRO_ACCENT.usesAccent);
+        assertTrue(OverviewStyle.MG.usesAccent);
+        assertFalse(OverviewStyle.RETRO.usesAccent);
+        assertFalse(OverviewStyle.CARTOON.usesAccent);
+        assertFalse(OverviewStyle.NIXIE.usesAccent);
+    }
+}