Master-playlist requests mint a fresh atproto TID; that sid is embedded in every sub-playlist + getVideoBlob URL the playlist references, so follow-up media-playlist + segment fetches can be correlated back to one playback session. View-count accounting will hang off this later — this commit is just the plumbing. A caller-supplied sid is reused after passing syntax.ParseTID, so a player that follows our master-playlist URLs carries the same id through without us minting a new one each hop. Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>