Commercial banks continued to amass a record supply of mortgage securities during the second quarter of 2005, as the industry’s total holdings edged up to $913.41 billion at the end June. But after spurting up by some $34.32 billion in the first three months of the year, the most recent quarter’s gain of just $2.72 billion – or 0.3 percent – was modest. Since the middle of 2004, bank holdings of mortgage securities have increased…