feat(android): initialise Oboe runtime context

apps/chanora_flutter/android/app/src/main/AndroidManifest.xml

@@ -34,7 +34,7 @@
          related in-call audio routing operations. -->
     <uses-permission android:name="android.permission.MODIFY_AUDIO_SETTINGS" />
 
-    <!-- SDD-trace: cpal-on-Android research report; supports SCO/BLE
+    <!-- SDD-trace: Android Oboe voice backend; supports SCO/BLE
          headset routing on API 31+. Declared here so the platform
          allows querying / connecting to bonded Bluetooth audio devices
          for the voice session. -->

apps/chanora_flutter/android/app/src/main/kotlin/app/chanora/chanora_flutter/MainActivity.kt

@@ -29,9 +29,9 @@ class MainActivity : FlutterActivity() {
     companion object {
         /**
          * JNI entry point implemented in `chanora_bridge::android_init`.
-         * Initialises `ndk_context` with our Activity so cpal-on-Oboe can
-         * find Android audio services when `chanora_audio` starts the
-         * capture / playback streams.
+         * Initialises `ndk_context` with our Activity so the direct Oboe
+         * backend can find Android audio services when `chanora_audio`
+         * starts the capture / playback streams.
          *
          * Trace: SDD-105 (AndroidJniBootstrap). Signature must remain stable;
          * the Rust side declares the matching `extern "system"` symbol.