Add the three missing VDES decoder components per ITU-R M.2092-1:
- turbo.rs: Turbo FEC decoder with dual 8-state RSC constituent
encoders, BCJR/MAP iterative decoding (8 iterations), QPP
interleaver, and rate-1/2 depuncturing
- crc.rs: CRC-16-CCITT validation (poly 0x1021, init 0xFFFF) for
decoded link-layer frames
- link_layer.rs: Structured parsing of M.2092-1 link-layer frames
(Messages 0-6) including station addressing, ASM identification,
geographic bounding boxes, and ACK/NACK reporting
The main decode pipeline now attempts turbo decoding first with CRC
validation, falls back to Viterbi when turbo fails, and reports
crc_ok=true when either path validates. 27 tests covering all new
modules.
https://claude.ai/code/session_01SJSN7cv3zoL1xNcb8ex2zY
Signed-off-by: Claude <noreply@anthropic.com>
