Drop per-task port blocks; previews use any free loopback port

internal/store/preview.go

@@ -43,6 +43,36 @@ func (s *Store) SetPreview(ctx context.Context, p api.Preview, actor string) ([]
 			return err
 		}
 
+		rows, err = tx.QueryContext(ctx, `
+			DELETE FROM previews WHERE port = ? AND task_id != ? AND task_id IN (SELECT id FROM tasks WHERE status = ?)
+			RETURNING task_id, name, (SELECT project_id FROM tasks WHERE id = previews.task_id)
+		`, p.Port, p.TaskId, string(api.TaskStatusActive))
+		if err != nil {
+			return err
+		}
+		taken := []api.Event{}
+		for rows.Next() {
+			taskID, name, project := "", "", ""
+			err = rows.Scan(&taskID, &name, &project)
+			if err != nil {
+				rows.Close()
+				return err
+			}
+			taken = append(taken, api.Event{Kind: "preview.taken", ProjectId: &project, TaskId: &taskID, Actor: actor,
+				Payload: map[string]any{"name": name, "port": p.Port, "by_task_id": p.TaskId}})
+		}
+		rows.Close()
+		err = rows.Err()
+		if err != nil {
+			return err
+		}
+		for _, ev := range taken {
+			err = emit(ev)
+			if err != nil {
+				return err
+			}
+		}
+
 		_, err = tx.ExecContext(ctx, `INSERT INTO previews (`+previewColumns+`) VALUES (?, ?, ?, ?)`, p.TaskId, p.Name, p.Port, formatTime(p.CreatedAt))
 		if err != nil {
 			return err