fix(nests): platform-side audio robustness — focus, AEC, route obs, network handover

Four follow-up fixes from the post-audit review (#4 / #5 / #6 / #7).

#6 AcousticEchoCanceler / NoiseSuppressor / AGC on the AudioRecord
   session. The VOICE_COMMUNICATION input source engages the platform
   echo canceller automatically on most modern Android devices, but a
   small set of older / OEM-customised devices only attach AEC under
   MODE_IN_COMMUNICATION — which an audio-room app deliberately
   avoids. Attaching the standalone audiofx effects to the
   AudioRecord's session id covers those devices without rerouting
   through the call audio path. All three are best-effort and a no-op
   on devices where the source already engages them.

#4 Real audio focus handling. The previous OnAudioFocusChangeListener
   was a no-op based on the assumption that the OS would auto-duck
   us; it doesn't (CONTENT_TYPE_SPEECH streams aren't auto-ducked).
   Inbound phone calls were mixing on top of room audio.
   - New `NestAudioFocusBus` (commons) — process-wide enum signal,
     decoupled from android.media so commons stays platform-free.
   - NestForegroundService translates AUDIOFOCUS_GAIN / LOSS_TRANSIENT*
     / LOSS into the bus enum.
   - NestViewModel observes the bus and silences both the listener
     playback (effective listen-mute = user OR focus) and the
     broadcast mic (effective mic-mute = user OR focus). User-visible
     mute states stay the user's choice so a focus regain restores
     them automatically.
   - The pipeline keeps running while focus is lost (decoder, capture,
     network) so unmute is sample-accurate when the call ends.

#5 AudioDeviceCallback observability. Registers a callback in
   NestForegroundService that logs Bluetooth / wired / USB headset
   attach + detach with device type + name. Doesn't drive playback
   decisions — Android's auto-routing handles route swaps — but
   makes "audio cut out when I plugged in headphones" reports
   correlatable with a concrete event for the first time.

#7 Network-change → fast reconnect. Without this, a Wi-Fi → cellular
   handover left the QUIC connection sitting on a now-dead socket
   until its PTO fired (~30 s) before the wrapper noticed. Now:
   - New `NestNetworkChangeBus` (commons) — collapses bursts of
     onLost/onAvailable into a single recycle event.
   - NestsListener + NestsSpeaker grow `recycleSession()` (default
     no-op); the reconnecting wrappers override to close the inner
     session so their orchestrator opens a fresh one.
   - NestForegroundService registers a default-network callback;
     suppresses the first onAvailable (registration callback)
     and only publishes on actual default-network changes.
   - NestViewModel observes the bus and calls recycleSession on
     both wrappers. The SubscribeHandle re-issuance pump (listener)
     and the hot-swap publisher pump (speaker) cut existing
     subscriptions / broadcasts onto the new session as soon as
     it lands — same paths the JWT-refresh recycle uses.
   - Manifest gains ACCESS_NETWORK_STATE for
     registerDefaultNetworkCallback.

nestsClient/src/commonMain/kotlin/com/vitorpamplona/nestsclient/NestsSpeaker.kt

@@ -66,6 +66,27 @@ interface NestsSpeaker {
      */
     suspend fun startBroadcasting(onLevel: (Float) -> Unit = { /* no-op */ }): BroadcastHandle
 
+    /**
+     * Force the underlying transport / MoQ session to be torn down and
+     * a fresh one opened in its place — without permanently closing
+     * this speaker. Mirror of [NestsListener.recycleSession]; same
+     * use case (network handover) and same default no-op for non-
+     * reconnecting implementations.
+     *
+     * The reconnecting wrapper from
+     * [connectReconnectingNestsSpeaker] overrides to close the
+     * inner speaker so its orchestrator opens a fresh session.
+     * For moq-lite speakers, the long-lived
+     * [com.vitorpamplona.nestsclient.audio.NestMoqLiteBroadcaster]
+     * keeps capturing through the recycle and the
+     * [BroadcastHandle.swapPublisher]-based pump retargets onto
+     * the new session's publisher with no audible gap.
+     */
+    suspend fun recycleSession() {
+        // no-op — only the reconnecting wrapper has anywhere to
+        // recycle to.
+    }
+
     /** Tear down the MoQ session + transport. Idempotent. */
     suspend fun close()
 }