feat(playback): draw catch-up programmes as seek-bar segments (#1750)

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

@@ -0,0 +1,9 @@
+---
+type: feature
+area: playback
+---
+
+Catch-up and timeshift playback now draws the programmes of the archive window
+on the player's seek bar, one segment per programme. Hovering the bar shows the
+programme title with the time, so you can jump to the next show in an M3U
+recording that spans several.

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

@@ -1,8 +0,0 @@
----
-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.