Fix channel worker stalling when stopping ffmpeg with unread stdout

CHANGELOG.md

@@ -20,6 +20,10 @@ All notable changes to this project are documented in this file.
 
 ### Fixed
 
+- Stopping ffmpeg (on every proactive URL refresh) no longer stalls. The worker stops reading ffmpeg's stdout when it
+  breaks out to refresh, and asyncio's `Process.wait()` does not return until every pipe reaches EOF, so `stop()` always
+  ran into the terminate timeout ("did not exit in time, killing it") and could leave a channel worker stuck for good,
+  silently ending that channel's stream. `stop()` now drains the leftover stdout while waiting for ffmpeg to exit.
 - `/stream/{channel_id}` now forces the connection closed after each response (`Connection: close`) instead of
   allowing keep-alive. Jellyfin's M3U tuner client (`SharedHttpStream`) was reusing a pooled keep-alive connection
   still mid-stream from an earlier request and reading raw MPEG-TS bytes as if they were a fresh HTTP response,