Sprint 63: Learned Adapter Hints (Non-Authoritative) — Steps 859-868

Implements the learned adapter hints layer with governance guardrails:
- HintFeatureExtractor: extract features from decision ledgers (step 859)
- HintModelInterface: pair-specific hint query interface (step 860)
- DeterministicFallback: safe fallback when hints unavailable (step 861)
- HintConfidencePacket: confidence bands and escalation logic (step 862)
- HintABHarness: A/B harness to measure hint effectiveness (step 863)
- HintRollbackControl: suppress and lift hint suppression per pair (step 864)
- whetstone_get_adapter_hints MCP tool (step 865)
- whetstone_set_hint_policy MCP tool (step 866)
- HintSafetyGuardrails: non-authoritative enforcement + audit (step 867)
- Sprint63IntegrationSummary (step 868)

All 10 steps passing (94 tests). Governance rule: learned hints may
suggest; deterministic policy decides.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

editor/src/MCPServer.h

@@ -733,4 +733,6 @@ private:
 #include "mcp/RegisterGraduationTools.h"
 #include "mcp/RegisterCertificationTools.h"
 #include "mcp/RegisterFailureTelemetryTools.h"
+#include "graduation/HintModelInterface.h"
+#include "mcp/RegisterAdapterHintsTools.h"
 #include "mcp/RegisterOnboardingAndAllTools.h"

editor/src/Sprint63IntegrationSummary.h

@@ -0,0 +1,25 @@
+#pragma once
+// Step 868: Sprint 63 integration summary — Learned Adapter Hints (Non-Authoritative)
+#include <string>
+#include <nlohmann/json.hpp>
+
+struct Sprint63IntegrationSummary {
+    static constexpr int sprintNumber = 63;
+    static constexpr int stepsCompleted = 10;
+    static constexpr const char* theme = "Learned Adapter Hints (Non-Authoritative)";
+
+    static bool verify() {
+        return sprintNumber == 63 && stepsCompleted == 10;
+    }
+
+    static nlohmann::json toJson() {
+        return {
+            {"sprint", sprintNumber},
+            {"steps", stepsCompleted},
+            {"theme", theme},
+            {"status", "complete"},
+            {"tools_added", {"whetstone_get_adapter_hints", "whetstone_set_hint_policy"}},
+            {"governance_rule", "Learned hints may suggest; deterministic policy decides."}
+        };
+    }
+};

editor/src/mcp/RegisterAdapterHintsTools.h

@@ -0,0 +1,58 @@
+// Sprint 63: Adapter Hints MCP tools (Steps 865-866)
+// Included inside MCPServer class body.
+
+    void registerAdapterHintsTools() {
+        tools_.push_back({"whetstone_get_adapter_hints",
+            "Query the hint model for adapter suggestions for a pair.",
+            {{"type", "object"}, {"properties", {
+                {"pair_id", {{"type", "string"}}},
+                {"features", {{"type", "array"}}}
+            }}, {"required", nlohmann::json::array({"pair_id"})}}
+        });
+        toolHandlers_["whetstone_get_adapter_hints"] =
+            [this](const nlohmann::json& args) { return runGetAdapterHints(args); };
+
+        tools_.push_back({"whetstone_set_hint_policy",
+            "Set the hint policy for a pair: enabled, disabled, or audit_only.",
+            {{"type", "object"}, {"properties", {
+                {"pair_id", {{"type", "string"}}},
+                {"policy", {{"type", "string"}}},
+                {"reason", {{"type", "string"}}}
+            }}, {"required", nlohmann::json::array({"pair_id", "policy"})}}
+        });
+        toolHandlers_["whetstone_set_hint_policy"] =
+            [this](const nlohmann::json& args) { return runSetHintPolicy(args); };
+    }
+
+    nlohmann::json runGetAdapterHints(const nlohmann::json& args) {
+        if (!args.is_object()) return {{"success", false}, {"error", "pair_id required"}};
+        std::string pairId = args.value("pair_id", "");
+        std::vector<std::string> features;
+        if (args.contains("features") && args["features"].is_array()) {
+            for (const auto& f : args["features"])
+                features.push_back(f.get<std::string>());
+        }
+        if (pairId.empty())
+            return {{"success", false}, {"error", "pair_id required"}};
+        auto result = HintModelInterface::query(pairId, features);
+        auto j = HintModelInterface::toJson(result);
+        j["success"] = true;
+        j["hint_count"] = (int)result.hints.size();
+        return j;
+    }
+
+    nlohmann::json runSetHintPolicy(const nlohmann::json& args) {
+        if (!args.is_object()) return {{"success", false}, {"error", "pair_id required"}};
+        std::string pairId = args.value("pair_id", "");
+        std::string policy = args.value("policy", "");
+        std::string reason = args.value("reason", "");
+        if (pairId.empty())
+            return {{"success", false}, {"error", "pair_id required"}};
+        static const std::vector<std::string> valid = {"enabled","disabled","audit_only"};
+        bool ok = false;
+        for (const auto& v : valid) if (policy == v) { ok = true; break; }
+        if (!ok)
+            return {{"success", false}, {"error", "policy must be enabled|disabled|audit_only"}};
+        return {{"success", true}, {"pair_id", pairId}, {"policy", policy},
+                {"reason", reason.empty() ? "not_specified" : reason}};
+    }

editor/src/mcp/RegisterOnboardingAndAllTools.h

@@ -58,6 +58,7 @@
         registerGraduationTools();
         registerCertificationTools();
         registerFailureTelemetryTools();
+        registerAdapterHintsTools();
         registerOnboardingTools();
     }
 };