Controller: hold to show the secondary subtitle, dictionary entry navigation, standard button names (#312)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

src/core/services/ipc.test.ts

@@ -70,6 +70,9 @@ function createControllerConfigFixture() {
       nextAudio: { kind: 'button' as const, buttonIndex: 5 },
       playCurrentAudio: { kind: 'button' as const, buttonIndex: 7 },
       toggleMpvPause: { kind: 'button' as const, buttonIndex: 6 },
+      holdSecondarySub: { kind: 'none' as const },
+      previousEntry: { kind: 'none' as const },
+      nextEntry: { kind: 'none' as const },
       leftStickHorizontal: {
         kind: 'axis' as const,
         axisIndex: 0,