tsb/tsb.hpp holds the link, the handshake and command bytes, the guard
policy and SPM interlock, the boot geometry, act_min/comm_window and a
consteval builder for the 16-byte info block, whose BUILDSTATE and ATmega
marker bytes are now named rather than commented. Every tier's image is
byte-identical to before.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
