fix(mpv): stop loading the ytdl hook for media-server streams

Every URL the player opens is a media-server stream or a local file, so mpv's
bundled ytdl_hook has nothing to resolve. It still ran an on_load hook per
open and, whenever an open failed, spawned yt-dlp with the full stream URL in
its argv — access token included, readable through /proc on Linux. It also
added ~700ms to every failed open and buried the real "[stream] Failed to
open" line under three ytdl_hook errors.

mpv decides whether to load the builtin script inside mpv_initialize, so this
has to be an option set beforehand rather than a property set from Dart.
Verified against mpv 0.41: --ytdl=yes logs "Loading lua script
@ytdl_hook.lua", --ytdl=no never loads it.

Apple is deliberately excluded: the bundled libmpv is built without Lua, so
the option does not exist there and setting it would only print an mpv error
on every player init.

windows/runner/mpv/mpv_player.cpp

@@ -570,6 +570,12 @@ bool MpvPlayer::Initialize(HWND view) {
   // mpv's default handling would double-handle Play/Pause.
   mpv_set_option_string(mpv_, "input-media-keys", "no");
   mpv_set_option_string(mpv_, "osc", "no");
+  // Never resolve URLs through mpv's bundled ytdl_hook: Plezy only ever opens
+  // media-server streams and local files, the hook adds a per-open on_load
+  // round trip, and on a failed open it spawns yt-dlp with the access token in
+  // its argv. mpv decides whether to load the builtin script during
+  // mpv_initialize, so this must be an option, not a Dart setProperty.
+  mpv_set_option_string(mpv_, "ytdl", "no");
 
   if (!audio_only_) {
     // Let mpv use display/context detection instead of forcing HDR signaling.