feat(auto): append outgoing reply to MessagingStyle for brief confirmation

Before cancelling a conversation notification in response to an inline
reply, post one final update that appends the outgoing text to the
MessagingStyle history, attributed to the local user. This gives
assistants such as Android Auto a tick to observe the sent message in
the notification's message history and surface a 'reply sent' style
confirmation before markConversationRead cancels the notification.

Extract the 'me' Person construction into buildMePerson() and share it
between showGroupSummary and createConversationNotification. The
conversation builder now optionally takes an extraOutgoingMessage which
is appended to the MessagingStyle (actions and when-timestamp continue
to be anchored on the last incoming message).

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

core/testing/src/commonMain/kotlin/org/meshtastic/core/testing/FakeMeshServiceNotifications.kt

@@ -69,6 +69,8 @@ class FakeMeshServiceNotifications : MeshServiceNotifications {
 
     override suspend fun markConversationRead(contactKey: String) {}
 
+    override suspend fun appendOutgoingMessage(contactKey: String, text: String) {}
+
     override fun cancelLowBatteryNotification(node: Node) {}
 
     override fun clearClientNotification(notification: ClientNotification) {}