Player: quick chat box, danmaku notifications, the player panel, smooth subtitle lift

- Quick chat (Enter in the full player, whatever plays): a box at the
  bottom centre in the control bar's place, compact and widening with
  the text, sharing its draft with the chat panel; Enter sends, Esc or an
  empty Enter closes, it closes by itself after 8 s without typing (the
  draft stays). Keys go to it; the Enter that opened it no longer reaches
  a focused button. Typing never shows the cursor or the controls: the
  frame wakes only on real mouse movement and holds the controls hidden
  while the box or its echo is up. Your sent line shows as an echo (or
  flies as your own danmaku line); your own chat toast is not repeated.
- Subtitle lift: always for the box, for the control bar as a setting
  (off); 4 eased-out sub-pos steps 42 ms apart instead of one per frame.
- Notifications: Toasts / Danmaku (off by default): chat and short notices
  fly over the full player, problems stay toasts; every knob of the look
  plus boldness, persisted, with a live preview strip in Settings.
- Player panel: ⚙ → Player settings docks a foldable glass panel at the
  right (tracks, subtitle size and lift, picture, volume, notifications,
  controls) in place of the card; Esc closes it.
- Danmaku preview: the mock dialogue follows the lift; the stand-in page
  has the chat box too.

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

CHANGELOG.md

@@ -7,7 +7,7 @@ cut into a release: [docs/DEVELOPMENT.md](docs/DEVELOPMENT.md#changelog).
 
 ## Unreleased
 
-Links you put up are downloaded once for everyone, plus What's new and fixes for Windows, the relay and chat.
+Links you put up are downloaded once for everyone, quick chat and danmaku in the player, plus What's new and fixes for Windows, the relay and chat.
 
 ### Added
 
@@ -17,6 +17,10 @@ Links you put up are downloaded once for everyone, plus What's new and fixes for
 - Invite finds your internet address, lets you pick it or your home-network address, and says when your router needs the port forwarded
 - The password goes into an invite link only when you tick "Include the password in the link"
 - Starsync runs once: a link clicked while it is open goes to the open window
+- Quick chat: press Enter in the big player to type a message in a small box at the bottom, without opening the chat panel and without the mouse pointer or the controls popping up; it shares its draft with the chat panel, closes by itself when you stop typing, and subtitles move up out of its way
+- Danmaku notifications: chat, joins, leaves and Up next can fly across the top of the picture instead of popping up (Settings → Notifications & sounds → Notifications: Danmaku, off by default), with speed, how many at once, where, opacity, size, boldness, outline and avatars all adjustable and a live preview
+- Player panel: ⚙ → Player settings opens a panel at the right of the player that stays open while you watch, with tracks, subtitle size, picture, volume and notification settings
+- Subtitles can move up above the controls while they show (Settings → Player → Subtitles above the controls, off by default), and their size can be changed
 
 ### Changed