AMQP10::Protocol::Codec

Descriptors may be encoded either numerically (ulong code) or symbolically (§1.6). Map the symbolic names of every section and outcome we understand back to their numeric code so peers that describe by name interoperate.

Turns IO#read_byte's nilable return into the raising form AMQP10 always wants; not a passthrough over read_bytes, so it earns its keep.

Reads a 32-bit size field and validates it against the remaining payload, so a hostile oversized size cannot allocate or read past the buffer.

Zero-copy view into io's own backing buffer, advancing pos past it. The slice is only valid as long as the buffer is: callers decode and retire it synchronously, so -- unlike amq-protocol's Table.from_io -- it is never defensively copied when the source is writable.

Described values are skipped iteratively: a descriptor can itself be a described value, nested without bound in untrusted input, so recursing would let a crafted value exhaust the stack.

The slice from an earlier saved position up to io's current pos.

Shared with TransferCodec's direct-field writers below, and with client.cr/types.cr's direct-field performative senders -- a single implementation for the "described-list header" shape used throughout AMQP 1.0's wire format, not a generic Value/Array round-trip.