Codify the layer model settled with the user: an inner-to-outer ladder
engine -> market -> {measurement | strategy} -> backtest -> execution,
the research-process column beside the ladder, the shell outside. States
the import rule (inner never imports outer; measurement/strategy
siblings; column imported by no ladder crate; shell imports all;
dev-deps exempt), the six seams (five already ratified contracts —
C8/C24/C27/C18/C10-C13 — only the metric interface new), and an honest
Status recording the one hard production violation (engine -> analysis
via report.rs re-exports + the R-typed mc.rs fields) and its coupling to
the deferred #147.
Also restore the "### C19" header, deleted as collateral of ebe8568
(2026-07-03 cycle-0106 tidy); its body survived orphaned under C18. C28
cites C19, so the header must resolve.
refs #286
claude
1c49d5dce2