Protocol 12: Up next (a shared queue) and where the video comes from

Up next: a server-side queue anyone edits by item id (add at end or
next, move, remove, play now, skip); each item says who added it and
how it plays. At the real end the first item swaps in after the end
card's countdown, put up by whoever can (its adder for through-me links
and files, someone with access for Jellyfin, else anyone); items that
can't play are skipped with the reason. The next item's link is
resolved ahead. Greyed "Continues with" episodes below. A chip with the
controls opens it as a popover (leaf_widgets, local path dependency for
now); "Add to queue" next to Put it up everywhere.

Delivery: the server measures the source's rate, the media's bitrate
and each member's read rate; the members card shows a source line
(who passes it on, through what, keeping up or not, source left) and
each member's route and buffer. A slow source is told once per media.
A failed server fetch is announced to everyone.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -158,6 +158,32 @@ folder to Files, or fill Link).
 Put it up and the player opens. Not in a server, the buttons say Play
 and it plays for you alone ([Watch solo](#getting-started)).
 
+### Up next (the queue)
+
+In a server (solo too), anything can wait its turn instead of going up
+now: **Add to queue** on the Link page (in the way you picked), or
+right-click a Jellyfin card or episode, a video in Files or a recent link
+for **Add to queue** / **Play next**; the Jellyfin details panel has a
+queue button (right-click it to play next). A link is checked first, like
+Put it up. Everyone shares one Up next and anyone can change it; what
+you added stays when you leave.
+
+In the player, **Up next · title** sits top right with the controls: ▶
+plays it now, the title opens the queue: drag rows to reorder, hover a
+row to play it now (▶) or remove it (×), paste a link in the field or
+drop a link or a video on it to add. When a video ends, a card shows
+what is up next with a 10 s countdown (Cancel stops it on your screen)
+and it plays; `>` or Shift+N plays it at once. Under the queue,
+**Continues with** shows the next episodes of the Jellyfin series
+playing (greyed: they play only once Up next is empty); **+** adds one,
+**Clear** drops them for this episode.
+
+A link you pass on ("through me") or a file of yours can only be played
+by your app: if you left when its turn comes, it is skipped ("Skipped …:
+Foxyz left"). A Jellyfin item needs someone with an account on that
+server. Up next is kept by the server while it runs; restarting the
+server empties it.
+
 ## Dedicated server
 
 For an always-on box (no display needed): the release tarball also contains
@@ -302,7 +328,7 @@ Watching:
 - Friends without an account watch through the server: whoever put the
   item up passes it on automatically, with their own sign-in, which never
   leaves their computer (only the current item, only to people in the
-  session). They show "via host" in the member list (click the avatars). When the app hosts,
+  session). They show "via server" in the member list (click the avatars). When the app hosts,
   or a dedicated server has its own login (`--jellyfin <file>`, see
   [docs/ARCHITECTURE.md](docs/ARCHITECTURE.md), Jellyfin relay), the server
   fetches it itself instead.
@@ -362,6 +388,18 @@ streams or DRM-protected video (use "Everyone fetches it" for live).
 Your upload has to beat the video's bitrate: a 25-minute 2 GB episode is
 about 11 Mbit/s.
 
+The member list (click the avatars) shows where the video comes from on
+top: who passes it on, or that the server fetches it, everyone plays the
+link, or everyone streams it from Jellyfin, with how many watch through
+the server and, for a relay, how fast it arrives against what the video
+needs (the bar's mark; past it is keeping up). It turns amber when the
+source is too slow or reconnecting, red when it left (the others play
+out what the server already has), and whoever passes it on is told once
+when their upload is too slow. Each member's line says how they get it
+("via server" with their speed, or "direct") after a dot for their
+buffer: green enough to play on, amber low, red empty. A red dot on one
+member while the source keeps up is their own connection.
+
 ## Video quality and shaders
 
 Each viewer can run mpv GLSL shaders on their own picture; nobody else is