Implements the 13 record types from `[MS-NMF]` §2.2 (Version, Mode, Via,
KnownEncoding, ExtensibleEncoding, Unsized/SizedEnvelope, End, Fault,
UpgradeRequest/Response, PreambleAck, PreambleEnd) over a `net.tcp` channel.
Includes the `Multibyte Int31` length codec (LEB128-style 7-bit groups
over a 31-bit unsigned range, max 5 bytes; rejects negative input and
overflow), plus an `encode_preamble` helper that emits the canonical ASB
connect record sequence (`Version 1.0 → Duplex → Via $uri →
BinaryWithDictionary → PreambleEnd`).
Pure codec — no I/O. Encoders write into a `Vec<u8>`; decoders parse
from a `&[u8]` slice and return the consumed-byte count alongside the
record. Higher-level connect/request/response orchestration stays in the
M5 ASB client (`mxaccess-asb`, F25).
24 new unit tests cover round-trip for every record type, multibyte-int31
boundary cases (0, 1, 127, 128, 16383, 16384, 200, i32::MAX), preamble
emission against the canonical ASB sequence, byte-layout pinning for
Version/Mode/KnownEncoding, and rejection of unknown record/mode/encoding
bytes plus truncated sized-envelope frames.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Joseph Doherty
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