Function render_row 

pub fn render_row(row: &MessageRow, team: &TeamSnapshot) -> String

Format a single row for the mailbox pane. Kept terse: [from] text on one line — no timestamps, no recipient (the tab tells you the recipient class). Multi-line bodies are flattened with a space so a single message stays one row in the pane. team is consulted via agent_label so senders with a display_name show their human label; unknown senders (cross-project, system) fall back to the canonical id verbatim.