Initial whetstone_RSA architecture and C++ scaffold

include/whetstone_rsa/diagnosis_engine.h

@@ -0,0 +1,25 @@
+#pragma once
+
+#include "whetstone_rsa/probe_registry.h"
+
+namespace whetstone::rsa {
+
+class DiagnosisEngine {
+public:
+    explicit DiagnosisEngine(ProbeRegistry probe_registry);
+
+    [[nodiscard]] GateDiagnosis diagnose(const GateDefinition& gate_definition,
+                                         const GateEvidence& evidence,
+                                         const PolicyContext& policy_context) const;
+
+private:
+    [[nodiscard]] static PolicyRecommendation recommend_policy(const GateDefinition& gate_definition,
+                                                               const GateEvidence& evidence,
+                                                               const PolicyContext& policy_context,
+                                                               FailureClass primary_failure_class,
+                                                               const std::vector<Intervention>& interventions);
+
+    ProbeRegistry probe_registry_;
+};
+
+}  // namespace whetstone::rsa