Warner Bros. Discovery, known affectionately here at Faultline as WarnerDisco (trademark pending), is one step closer to being a merged reality as AT&T announced the spin-off of WarnerMedia in a bid to maximize the value of media assets ahead of completion. If (not when) the transaction closes next quarter, subject to regulatory approvals, the spin-off will distribute 71% of the newly merged entity among AT&T shareholders (instead of AT&T itself retaining 71% as initially planned), with the remaining 29% distributed among Discovery shareholders. The good news for AT&T is that the spin-off generates a return of $43 billion. The bad news is that AT&T’s dividend yield (the amount paid out to shareholders relative to share price) has tanked as a…