test(multiplayer): verify two-player proposal round trip

server/store/proposal_sql.go

@@ -3,6 +3,7 @@ package store
 import (
 	"context"
 	"database/sql"
+	"encoding/json"
 	"fmt"
 	"time"
 
@@ -13,6 +14,10 @@ const ProposalInsertSQL = `INSERT INTO proposals
     (proposal_id, playlist, state, expires_at, revision, match_region, match_protocol)
 VALUES ($1, $2, 'OPEN', $3, 0, NULLIF($4, ''), NULLIF($5, 0))`
 
+const ProposalOutboxInsertSQL = `INSERT INTO outbox
+    (event_id, aggregate_type, aggregate_id, revision, event_type, payload)
+VALUES ($1, 'proposal', $2, 0, 'proposal_changed', $3)`
+
 // CreateProposal atomically claims the queue tickets and creates the proposal.
 // Every statement runs inside the same SERIALIZABLE retry callback; callers
 // must never publish a proposal from a cache-only candidate list.
@@ -27,6 +32,7 @@ func CreateProposal(ctx context.Context, db *sql.DB, proposal domain.Proposal, t
 		if _, err := tx.ExecContext(ctx, ProposalInsertSQL, proposal.ProposalID, proposal.Playlist, proposal.ExpiresAt, proposal.Region, proposal.Protocol); err != nil {
 			return err
 		}
+		players := make([]string, 0, len(proposal.Participants))
 		for _, participant := range proposal.Participants {
 			ticketID := ticketIDs[participant.PlayerID]
 			if participant.PlayerID == "" || ticketID == "" {
@@ -46,6 +52,17 @@ func CreateProposal(ctx context.Context, db *sql.DB, proposal domain.Proposal, t
 			if changed != 1 {
 				return fmt.Errorf("queue ticket claim lost")
 			}
+			players = append(players, participant.PlayerID)
+		}
+		payload, err := json.Marshal(map[string]any{
+			"event": "proposal_changed", "revision": uint64(0), "resource_id": proposal.ProposalID,
+			"occurred_at": now, "state": string(proposal.State), "player_ids": players,
+		})
+		if err != nil {
+			return err
+		}
+		if _, err := tx.ExecContext(ctx, ProposalOutboxInsertSQL, proposal.ProposalID, proposal.ProposalID, payload); err != nil {
+			return err
 		}
 		return nil
 	})