ExoPlayerCore emitLog() forwards native diagnostics (init, tracks,
tunneling, watchdog, errors, framerate, audio focus) to Dart via the
existing log-message event when debug logging is enabled. URIs are
redacted before forwarding. setLogLevel method channel wires into the
existing debug toggle in video_player_screen.
Logs screen now shows a device info header (app version, OS, model,
TV mode) and includes it in copy/upload output.