checkPayloadDepth is an iterative header walk run by decodeDocumentPayload before the formatter and by
encodeDocumentPayload on the formatter's bytes; the two plain-decode inspection doors call it first. The plain
formatter's encoder depth is set above the limit so the walk decides. Tests: the C# bounds vectors, the walk's
header and scalar rules, the owner, the inspector, the legacy version inference, and the mesh network doors;
test:pack:ts denies decoder-shaped exports by enumerating the packed entries.
Builds and passes untested at this commit (verification runs on Yggdrasil next).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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