With Apple Inc.’s iPad firmly established as the biggest thing in tablet computing, rival companies are competing by thinking small, delivering less-expensive mini-tablets. Which brings us to the new Galaxy Note from Samsung Corp., a mini-tablet computer that doubles as a high-end smartphone, and features a stylus-based handwriting recognition system. It’s a capable hybrid device, but its unusual design and unreliable handwriting feature suggest that the Note’s future is as limited as its screen size.