Denver’s front office is stuck between a mountain and a hard place. Executive vice president of player personnel Jon Wallace and executive vice president of basketball operations Ben Tenzer did a lot of things right on paper last year, even if vice chairman Josh Kroenke got the love in the NBA Executive of the Year voting. Trading Michael Porter Jr. and a future first-round pick for Cam Johnson, acquiring Jonas Valanciunas for Dario Saric and signing Tim Hardaway Jr. and Bruce Brown to minimum contracts looked like moves that maximized the championship chances this season. Repeating the feat won’t be easy. After Nikola Jokic reiterated his desire to be a Nugget “forever,” offering the franchise cornerstone the maximum four-year extension worth nearly $280 million is the only obvious decision in the brain-trust trio’s second summer after disaster struck. Jamal Murray was the only member of Denver’s starting five who didn’t miss a significant stretch of the regular season.…