Formalizes the CEX-010 E-feed account plane (protocol + InMemoryZincPlane +
real plane). This code flew 33h on UV-PRIME flight-1 via the vendored copy
(T0-DEVIATION mid-edit vendoring) but was never committed upstream — the
2026-07-11 clean vendor_sync regressed it and broke the E-feed at boot
(AttributeError publish_account). Committing the flight-proven bytes closes
the vendor-law gap. Authorship: pre-existing WIP in /mnt working tree
(T0-era, likely codex), committed verbatim by Fable for vendor integrity.
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