WE SLIP INTO REVERIE. The traditional death notices along the passages and vaporetto stops around Venice have more faces than usual. The blue and yellow flag of Ukraine flaps in the cold breeze blowing off the lagoon. The carnival masks stare from shop windows at the face masks of those on the other side of the glass. Mingling with the throngs of holiday tourists, an art world sweeps in on boats and trains, buses and planes into the Most Serene Republic for the professional days of the fifty-ninth Biennale di Venezia after a long pandemicked wait of three years, and amid a war of aggression in