Checkpoint source 7 workflows and in-progress diagram authoring redesign

Preserve current core, source, REST, desktop, recovery, documentation and validation work, including AGENTS.md and the development summary. This is a work-in-progress checkpoint: the new compact palette has outstanding compilation errors and native acceptance; earlier passing gates retain their documented scope.

crates/oa-server/src/lib.rs

@@ -3,6 +3,9 @@ pub mod error;
 mod routes;
 pub mod store;
 
+#[cfg(test)]
+mod preparation_http_tests;
+
 use axum::{
     Router,
     extract::{DefaultBodyLimit, Request, State},