BEIRUT — Thousands of protesters poured onto the streets in towns and cities across Syria after prayers on Friday, sustaining their challenge to President Bashar al-Assad’s regime for a 10th week despite a continued military crackdown in which more than 1,000 people have died. Activists dedicated this week’s protests to the army, dubbing the day “Guardians of the Homeland Friday” in an attempt to woo the military to the side of the demonstrators.