Session resume falls back to sample radio; yt-dlp resume missing

[pythrick]

When I close and reopen cliamp with no args, it often comes back on the sample radio playlist instead of where I left off.

What I expected:

• reopen to the same playlist
• same track selected
• resume time where possible

What I saw:

• app starts on https://radio.cliamp.stream/streams.m3u
• previous playlist is gone for that session

Repro:

1. Start cliamp with a playlist (local files or yt-dlp URL).
2. Play a track for a bit.
3. Quit.
4. Start cliamp again with no args.

I also hit this with yt-dlp tracks: playlist restore would fail, and position resume did not happen.

I tested a local patch that fixed it by:

• persisting full session state (tracks, current index, shuffle/repeat) on exit
• restoring that state on startup when no positional args are passed
• allowing yt-dlp position resume through the existing seek-by-restart path

If this direction makes sense, I can open a PR.