Publish a safety-first Arduino learning course

[devkyato]

Summary

• turn the sketch collection into a progressive six-lesson Arduino Uno course
• add per-lesson objectives, pin maps, commands, verification steps, and challenges
• add hardware safety, setup, serial/Bluetooth, and troubleshooting guides
• refactor all seven sketches to remain responsive without blocking pattern delays
• make motor commands fail safe, and make Exercise F require a new command after emergency-stop release
• add official Arduino compilation CI and a deterministic offline course archive

Local verification

• all 7 sketches compiled individually for Arduino Uno with PlatformIO / Arduino AVR
• python tools/build_release.py produced an archive containing all 7 sketches
• git diff --check passed

Hardware

Not hardware-tested. Motor-driver requirements and the distinction between compile and hardware verification are explicitly documented; physical validation is tracked as follow-up work.