A joining member's player always called loadVideo(itemId, 0, false),
hardcoding a resume position of 0. Since a party's Emby stream is one
shared transcode session (PartyStreamService, keyed by partyId alone),
a newcomer's hls.js requesting segments from position 0 against a
session that already progressed well past that forces Emby to
seek/restart the shared transcode - stalling playback for every
member, host included, right as the newcomer joins.
Seed the initial resume position from the host's last-reported
position (already available in party.members) instead, so the first
segment request lands near where the shared session already is.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
