Preserve owning categories in public errors

docs/roadmap/implementation.md

@@ -147,6 +147,11 @@ for their respective later units.
 preserve `errors.Is`/`errors.As`, existing capacity metadata, exhaustion and
 provider projections, and cancellation identity.
 
+Completion: public projection preserves the owning operation alongside nested
+causes and specialized projections. Root and generation tests pass on Go 1.27.3;
+two use-case preparation-classification tests await the direct preparation
+marker specified below.
+
 ## Stage 5: Retain Successful-Response Read Failures
 
 **Catalog:** 8. **Files:** `internal/llm/openai_compatible_client.go` and focused