BEIJING — China’s first domestically built aircraft carrier slipped into the sea for the first time on Wednesday, after days of publicity celebrating the impending launch as a milestone in President Xi Jinping’s drive to extend China’s military reach far beyond its shores. Senior military and government officials watched as a Champagne bottle was smashed on the bow and as the 1,033-foot gray hull of the carrier eased into the water at Dalian, a northeastern port, Chinese military news media reported. China launched its first aircraft carrier, the Liaoning, in 2011, after buying and equipping its rusting Soviet-era hull from Ukraine in 1998. [...] the launch conveyed that China intended to build a navy that could not be beaten by other Asian countries, said Patrick Cronin, senior director of the Asia-Pacific Security Program at the Center for a New American Security in Washington.