Two faults, both present since v0.0.1, both found and confirmed on a device.
Audio track (DR-258). Jellyfin builds a transcode around one AudioStreamIndex,
so the alternate tracks are not in the stream that arrives — but the native
path only ever called setAudioTrack(n), which indexes ExoPlayer's audio track
*groups*. On Android that is the common case, since any source whose default
audio codec the device cannot decode is transcoded: logcat showed ExoPlayer
holding `Audio tracks: 1` while the menu listed every track in the file, so
each selection warned `Invalid audio track index` and was dropped, leaving the
default track playing with nothing in the UI saying so.
determine_audio_track_switch_strategy now decides by whether the stream in
front of the engine carries the track at all — a direct play still selects in
place, a transcode is re-negotiated at the chosen index and resumed. Where it
resumes is the player's answer rather than the UI's: the native path has no
<video> element to read, so it sends no position, and defaulting that to zero
re-opened the film at the beginning (caught on device before it shipped).
Subtitles (DR-259). The URL was missing its `Stream.` route segment, so every
sideloaded subtitle 404ed; since media3 1.5 a sideloaded text track only
becomes a track group once its file is parsed, so 42 failed fetches left
ExoPlayer with no text tracks and selection warned `available: 0`. Verified
against a live server: the built URL answers 404, the corrected one 200. The
tests that should have caught this asserted the shape of a mock helper that
restated the format string instead of the URL the app requests — so the new
test drives the repository itself, and failed red on the old URL.