Replace the native <video controls> element with a custom player.
Videos now fill the lightbox media area edge-to-edge on black instead
of sitting in a padded, rounded box, with an auto-hiding control bar
over a bottom gradient (2.5s idle, always visible while paused):
play/pause, drag scrubber with buffered ranges, time readout, volume
slider with session-persisted volume/mute, playback speed (0.25-2x),
loop, and fullscreen.
Click toggles playback, double-click toggles fullscreen. Keyboard:
Space play/pause, M mute, F fullscreen, L loop, Shift+Left/Right seek
5s, Up/Down volume (unmutes) — plain arrows still navigate between
media, and all player keys are ignored while typing in the info-panel
inputs. Videos autoplay on open, falling back to paused-with-controls
if the webview blocks it.
