docs(adr-066): record 4XX/5XX wildcard projection mapping (OAI-13)

docs/architecture/decisions/066-from-jsonschema-as-http-adapter.md

@@ -134,6 +134,21 @@ The
 difference is purely the input shape: a full document vs. a single
 endpoint.
 
+### Response-key wildcards (review 002 OAI-13)
+
+`from_openapi` projects OpenAPI response keys onto `HTTP_<status>` error
+codes, which require a concrete status. Class wildcards map to the first
+legal concrete status in their implied range: `4XX` → `HTTP_400`, `5XX`
+→ `HTTP_500`. The declared payload schema of the wildcard response is
+carried by the projected entry. `default` has no implied status range,
+so it is not projected (it would advertise an `HTTP_0` code that can
+never match a callback status) — unmapped upstream statuses surface as
+the synthesized `HTTP_<actual>` at call time regardless. A concrete
+status key always outranks a wildcard covering the same range, in both
+error projection and the success sweep (SSE detection +
+output-schema selection), where the precedence order is: concrete 2XX
+statuses, then `2XX`, then `default`.
+
 ## Consequences
 
 **Positive**: