Returning to the desktop window with the chrome still up left arrow keys
navigating the OSD instead of seeking: the first press seeked and silently
moved focus onto Play/Pause, and every press after that walked the buttons.
A window blur drops Flutter's primary focus to the root scope, so the player
screen's reclaim parks it on its own node. The only handoff back down to the
controls was the chrome visible->hidden transition, so with the OSD up nothing
reclaimed it -- hence the reported workarounds of letting the controls hide, or
moving the pointer off the player and back. Pointer exit normally hides the
chrome and masks this, which is why it only shows when the pointer stays over
the player while another window takes focus.
Hand the surface back on window re-activation, next to the existing hide-path
claim, and rename the helper since it is no longer hidden-chrome specific. The
claim runs synchronously because a platform callback is not guaranteed to be
followed by a frame; the screen's reclaim re-tests hasFocus when it runs, so the
two no longer compete.
Also gate the screen's self-heal so a directional key no longer pulls focus into
the OSD when "Video Player Navigation" is off -- Tab and select keep their path
in, which the ungated return value would otherwise consume with nowhere to go.
