Direct register access now reads through the named surface (hw::mcusr::wdrf.test(), hw::ucsr0b::write(...)) instead of the string form, matching how libavr itself is written. Zero-overhead: pure 740 B, tricks 658 B, asm 508 B unchanged, all byte-identical across modes, protocol green. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>