STILLWATER, N.Y. — The air was brisk, the student section was packed, and two high school soccer titans were locked in a showdown. You could have sworn it was a sectional playoff game. “The atmosphere was great,” junior Kendall Buechner said. But this was no postseason battle. The Stillwater and Mechanicville girls’ varsity soccer teams were meeting in an early-season September Wasaren League match on Tuesday. Both teams entered the contest as r…