Define the schema-first migration from dictionary actor traffic to
tagged `msgspec.Struct` payloads on both order-control boundaries.
Deats,
- normalize startup, status, identity and fill semantics;
- port paper, Binance, Kraken and IB through one contract;
- gate strict `tractor` payload specs on backend conformance;
- layer deterministic state tests with real actor IPC checks;
- split implementation into reviewable dependency-ordered commits.
(this patch was generated in some part by `opencode` using `gpt-5.6-sol` (`openai`))
Gud Boi