fix(ios): seed MO-active when a reader view registers

flutter_readium/CHANGELOG.md

@@ -7,6 +7,12 @@ Format follows [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ### Fixed
 
+- **iOS reader views mounted after `audioEnable` never applied the media-overlay
+  column-break CSS.** The MO-active flag lives on the reader view, so a view created
+  after audio was enabled started with it off and word highlighting could be split
+  across CSS columns for the rest of the session. The flag is now seeded from the live
+  navigator when a reader view registers, matching Android, where it lives on the
+  shared reader.
 - **Guided-navigation playback reported later reading-order positions on iOS and web.** Those
   platforms converted the matched reading-order index twice, so the second item was emitted as
   position 3. Locators now apply Readium's 1-based position convention exactly once.

flutter_readium/ios/flutter_readium/Sources/flutter_readium/FlutterReadiumPlugin.swift

@@ -119,6 +119,9 @@ public class FlutterReadiumPlugin: NSObject, FlutterPlugin, ReadiumShared.Warnin
   internal func registerAsCurrentReaderView(_ readerView: any ReadiumReaderView) {
     let old = currentReaderView
     currentReaderView = readerView
+    // `audioEnable` sets MO-active through an optional-chained `currentReaderView?`,
+    // so a view registering later must pick the flag up from the navigator itself.
+    readerView.setMOActive(timebasedNavigator is FlutterMediaOverlayNavigator)
     _ = old // released here, safely outside the write
   }