Classroom Digital Twin v2 runtime source

This bundle contains the corresponding runtime adapters, real Arduino String/Print,
Adafruit GFX and U8g2 sources used to build classroom-twin:2.0.
Build with Dockerfile (pinned official Emscripten 4.0.15 image). See link-flags.json.
Arduino String/Print: David A. Mellis, Hernando Barragan, Paul Stoffregen and contributors; LGPL-2.1-or-later.
Adafruit GFX: Adafruit Industries, BSD license in source headers and vendor/gfx/license.txt.
U8g2_for_Adafruit_GFX: olikraus, BSD license in source headers; font-specific notices are retained in u8g2_fonts.c.
Student sketches are compiled separately and are not part of this runtime source archive.
