For almost three quarters of a century, the rusty remains of HMS Tamar slept soundly on the floor of Hong Kong’s Victoria Harbor, as ferries and freighters went about their business overhead. The sunken wreckage of this disused British troopship, built in 1863 and scuttled in 1941, bothered no one — and no one bothered her. But in 2014, land reclamation on the shores of one of the world’s most expensive and densely populated cities put Hong Kong’s future on a collision course with its past, renewing a debate in some circles about how to reconcile the city’s evolving modern identity with its colonial history.