Originally created by: Caqil
The QR Beam codec (lib/features/qr_beam/domain/beam_codec.dart) has a well-defined "BB1" wire format described in comments. Let's promote it to a short docs/QR_BEAM.md:
- The header + data frame layout
- How the sender loops frames and the receiver reassembles
- Note that it's byte-identical to the web implementation
Good docs-first contribution — the source of truth is already in the file.
