feat(playback): Hybrid redesign of the shared player controls (#1709)

.changes/playback-hybrid-player-controls.md

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+---
+type: feature
+area: playback
+highlight: Redesigned player controls
+---
+
+The built-in player controls have a new look: a lighter dock that sits
+directly on the video, a round accent play button, the volume slider inline
+on wide players, a remaining-time counter, and a timeline that shows the time
+under your pointer before you seek.

.changes/playback-player-settings-panel.md

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+---
+type: feature
+area: playback
+highlight: Player settings panel
+---
+
+Audio, subtitles, quality, speed and aspect ratio now live in one settings
+panel behind a tune button. Wide players show subtitle and speed chips with
+their current value and slide the panel in beside the video; small players
+get a bottom sheet, and the tune button shows colored dots for anything
+turned on or changed.

.changes/playback-timeline-segments-model.md

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+---
+type: internal
+area: playback
+---
+
+The shared player timeline can draw chapter or programme segments with
+per-segment progress and a titled hover label; no player supplies segments
+yet, so the bar still renders as one segment.

.changes/playback-up-next-card.md

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+---
+type: feature
+area: playback
+highlight: Up next in the player
+---
+
+In the last minutes of a series episode the player shows an "Up next" card
+with the following episode's still, title and time remaining. One click
+plays it, and the switch keeps you in fullscreen.