Native streaming: unavailable-track guard pauses, but librespot keeps skipping through the whole queue

[LargeModGames]

Describe the bug
When librespot can't play any track on an account (the error audio key 0 1 block, librespot-org/librespot#1649), the stampede guard from #282 doesn't stop playback. It pauses after 3 consecutive Unavailable events, but librespot keeps loading the next track, so it still runs through the whole queue at machine speed. In a user's log it went to 17 failed tracks in 43 seconds with no input in spotatui, and CDN file loads started failing with rate limited. In a second session it went to 42 failures and Spirc state updates got 429 Too Many Requests. It only stopped when the queue ran out.

Cause
Spirc answers every PlayerEvent::Unavailable with handle_next (the Unavailable arm in connect/src/spirc.rs), and handle_unavailable also preloads the next track. A paused load_track still requests the audio key and the file, so the Pause the guard sends (UNAVAILABLE_ESCALATION_THRESHOLD in src/infra/player/events.rs) doesn't break the loop. DeferredPlayerCommand::Stop wouldn't either as written: it only calls player.stop() and leaves Spirc's state alone.

To Reproduce

1. Log in with an account affected by Audio key error librespot-org/librespot#1649 (it mostly hits newer accounts).
2. Start native playback of a playlist or album.
3. Every track logs error audio key 0 1 then Skipping to next track, and the consecutive N count in native playback unavailable keeps climbing past 3.

[17:59:16][spotatui::infra::player::events][INFO] native playback unavailable (track spotify:track:1JbrVh45evNhbm3R75aYzg, consecutive 3)
[17:59:16][spotatui_librespot_playback::player][INFO] Loading <I Really Want to Stay at Your House> with Spotify URI <spotify:track:7mykoq6R3BArsSpNDjFQTm>
[17:59:16][spotatui_librespot_core::audio_key][ERROR] error audio key 0 1
...
[17:59:35][spotatui_librespot_playback::player][ERROR] Unable to load encrypted file: Error { kind: ResourceExhausted, error: "rate limited for at least another 0 seconds" }
...
[17:59:55][spotatui::infra::player::events][INFO] native playback unavailable (track spotify:track:1Qtoq02RTZ4alrR7vJ4Lai, consecutive 17)

Expected behavior
After 3 consecutive unavailable tracks, native playback stops and no more keys or files are requested until the user starts something again.

Screenshots
N/A, log excerpt above.

Desktop (please complete the following information):

• OS: any
• Terminal: any
• Version: 0.42.0 (spotatui-librespot 0.8.3)

Additional context
The account-side key block is upstream and can't be fixed here. This issue is only about the guard. The fix probably belongs in the fork, either stopping Spirc's auto-advance after N consecutive unavailable tracks or exposing a Spirc stop the guard can call. The fork has issues disabled, so this one tracks it.