Add four SHA-256-truncation vectors covering ACK CRC computation with
incrementing attempt values (0..3) over a stable (timestamp, text,
sender_pub_key) triple. Demonstrates that each retry produces a
distinct expected CRC, fixing the algorithmic ambiguity noted in the
2026-04-01 audit.
Algorithm: SHA-256(timestamp(4) || txt_type_attempt(1) || text ||
sender_pub_key(32))[0..3] as little-endian uint32.
Validated against upstream meshcore-dev/MeshCore @ 1a7b361
(BaseChatMesh::composeMsgPacket, src/helpers/BaseChatMesh.cpp:407).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
swaitsandClaude Opus 4.7
2cf3d29fe1