KABUL, Afghanistan An Afghan official yesterday accused Pakistan's premier spy agency of organizing a recent assassination attempt on President Karzai of Afghanistan, the most serious in a string of allegations against Pakistan. The charge bodes ill for American efforts to get Pakistan's new government to work with Mr. Karzai's embattled administration to counter Islamic militants on their common border. Mr. Karzai escaped unharmed when assailants fired guns and mortars toward the president... ...