New authorship tiers for messages relayed into a session from Slack/Teams

Messages relayed into a session from Slack or Teams now carry one of three authorship tiers. session-user marks turns typed directly, with full standing. channel-participant marks turns relayed from a bound Slack, Teams, or shared-project channel, carrying the same standing as a same-session user message for that one action. unattributed marks background messages with no consent, and is treated accordingly. The prompt-construction functions building this section, Zts and Jts, are called from the live prompt-assembly path.