Initial whetstone_RSA architecture and C++ scaffold

include/whetstone_rsa/probes/confidence_threshold_probe.h

@@ -0,0 +1,15 @@
+#pragma once
+
+#include "whetstone_rsa/probe.h"
+
+namespace whetstone::rsa {
+
+class ConfidenceThresholdProbe final : public Probe {
+public:
+    [[nodiscard]] std::string id() const override;
+    [[nodiscard]] bool supports(const GateDefinition& gate_definition,
+                                const GateEvidence& evidence) const override;
+    [[nodiscard]] ProbeResult run(const ProbeRequest& request) const override;
+};
+
+}  // namespace whetstone::rsa