3classic 1.0.0

Initial independent release of 3classic, the Tatami-derived WordPress Classic Theme formerly named 3columns during local development. Includes compact masthead navigation, three-column layout, mobile off-canvas panels, and WordPress-native menus and widgets. Demo: https://wordpress.im/3classic/ . This is a separate project from wp-im/3columns. PHP and JavaScript syntax checks and installation-package integrity verified; this release does not claim WordPress.org review.