feat(embedded-mpv): configurable extra libmpv options and network auto-reconnect (#1515)

Extra libmpv options (Settings > Playback) reach every embedded engine off the command line (createSession array on Windows/macOS, a 0600 --include file on Linux native-view, a stdin preamble for the frame-copy helper); the keys the embed depends on are refused, and keys libmpv rejects are reported once per session. Dropped streams reload automatically (error, or ended on live) with 2 s -> 30 s backoff, six attempts per outage and a 30 s stability reset, only for a load that already played; engine failures stay terminal, a running recording is filed as interrupted and restarted after the reload, and an external subtitle file is re-added. Settings.embeddedMpvAutoReconnect (default on) opts out; the player shows 'Reconnecting... attempt N of M'.

Started by Bpl5966 in #1515 and finished by the maintainers in the same PR.

Co-authored-by: Bpl5966 <amine.b1959@gmail.com>
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

.changes/embedded-mpv-extra-options-reconnect.md

@@ -0,0 +1,11 @@
+---
+type: feature
+area: embedded-mpv
+highlight: Embedded MPV reconnects dropped streams
+---
+
+The embedded MPV player now reloads a live stream that drops mid-playback on
+its own, with increasing delays and an "attempt N of 6" line instead of a
+dead error screen; a new Settings > Playback toggle turns this off. The same
+section gains an advanced field for extra libmpv options (one key=value per
+line) that applies on every engine, with a short network timeout on by default.