Every other shell rule in layoutShell.ts already treats /player/* as
immersive; the amber "You're offline" strip was the one piece of chrome
still rendered above it. On the native Android video path that is not
cosmetic: VideoPlayer makes itself transparent so the ExoPlayer
SurfaceView behind the WebView is visible (DR-185), so a shell child that
still paints shows through the picture as a stripe across the top of the
film. Offline is also precisely when a downloaded video plays, so the
banner appeared when it was most in the way — and it offers the viewer
nothing to act on, since local playback needs no server.
The rule moves into the pure module as showOfflineBanner() rather than
staying an inline {#if} in the shell, so the immersive-route contract is
stated in one tested place.
TRACES: UR-003, UR-043 | DR-291 | UT-255
dtourolle
b98cbfe28a