Vendor media_kit_video 2.0.1 with the X11/EGL fix (hardware rendering on X11 with Flutter >= 3.38)

Flutter >= 3.38 keeps its EGL contexts on the raster thread, so
media_kit's video output found none on the platform thread and fell
back to software rendering (no shaders, ~5 fps) on X11. The patched
output opens Flutter's EGL display itself, steps GDK's GLX context aside
on X11 and releases its own context. Patch from a friend's agent, kept
in third_party/media_kit_video/starsync/. Wayland/NVIDIA still renders
on the GPU (checked); the X11 path was verified on the friend's machine.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

third_party/media_kit_video/starsync/README.md

@@ -0,0 +1,20 @@
+# Starsync's copy of media_kit_video
+
+Upstream: `media_kit_video` 2.0.1 from pub.dev (media-kit/media-kit, MIT,
+see ../LICENSE), vendored because upstream has not released since
+December 2025. The `example/` folder is left out.
+
+Patches (apply with `patch -p7` from the package root, as recorded):
+- `egl-platform-display.patch`: Flutter >= 3.38 keeps its EGL contexts on
+  the raster thread, so nothing is current on the platform thread where
+  the video output is created and media_kit fell back to software
+  rendering (no shaders, slow). The output now opens Flutter's EGL display
+  itself (eglGetPlatformDisplayEXT on the GDK X11/Wayland display) with
+  Flutter's config attributes; on X11 it steps GDK's GLX context aside
+  while its EGL context is in use (libglvnd refuses EGL on a thread
+  holding GLX), and releases its context instead of leaving it current.
+  Written by a friend's agent from a real X11 failure.
+
+To update: copy the new upstream version over this folder (minus
+`example/`), re-apply the patches, run the app under X11
+(`GDK_BACKEND=x11`) and Wayland.