feat(player): stream audio by default, add [audio] config for cookies and downloads

Long tracks (15 min to 1 hour+) didnt playbecause every song was fully
downloaded with yt-dlp into the cache before mpv was started.

Resolve the direct media URL with yt-dlp -g and hand it to mpv, so
playback starts within a couple of seconds. Cached files are still
used when present.

Add an [audio] section to config.toml:
- download: download songs to the cache before playing (default false,
  i.e. stream). Prefetch of the next track only runs in this mode.
- download_max_minutes: in download mode, songs longer than this (or of
  unknown length) are still streamed so 0 means no limit. default is le 15.
- cookies_from_browser: passed to yt-dlp as --cookies-from-browser for
  playback, for when YouTube asks to sign in or blocks a song.

README.md

@@ -169,9 +169,16 @@ popular_first = false
 accent = "cyan"       # a color name or a hex value like "#FF8800"
 
 [discord]
-client_id = ""        # change this for Discord RPC to work in Drift         
+client_id = ""        # change this for Discord RPC to work in Drift
+
+[audio]
+download = false              # false: stream songs; true: download to the cache first
+download_max_minutes = 15     # with download = true, longer songs are still streamed (0 = no limit)
+cookies_from_browser = ""     # e.g. "firefox" or "chrome"; passed to yt-dlp when YouTube blocks playback
 ```
 
+By default Drift streams songs, so playback starts right away even for hour long tracks. Set `download = true` to cache songs on disk first (this also prefetches the next song). If YouTube asks you to sign in or playback fails, set `cookies_from_browser` to the browser where youre logged into YouTube. If you alr have a `config.toml`, add the `[audio]` section by hand, since Drift never rewrites it.
+
 Set `DRIFT_CONFIG_DIR` or `DRIFT_STATE_DIR` to change where Drift keeps its config, playlists and session.
 
 ## Contributing